Method and apparatus for transmitting or receiving uplink feedback information in communication system

ABSTRACT

Disclosed are a method and an apparatus for transmitting or receiving uplink feedback information in a communication system. An operation method of a terminal may comprise receiving downlink control information (DCI) from a base station, the DCI including resource allocation information of a physical downlink shared channel (PDSCH); receiving data #n from the base station through the PDSCH indicated by the DCI; generating a hybrid automatic repeat request (HARQ) codebook including an HARQ response bit #n for the data #n and an HARQ response bit #n-1 for data #n-1 received from the base station before the data #n; and transmitting the HARQ codebook to the base station. Therefore, the performance of the communication system can be improved.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.17/853,692, filed on Jun. 29, 2022, which is a continuation of Ser. No.16/831,151, filed on Mar. 26, 2020 (now U.S. Pat. No. 11,412,497, issuedon Aug. 9, 2022), and claims priority to Korean Patent Applications No.10-2019-0035375 filed on Mar. 27, 2019, No. 10-2019-0081512 filed onJul. 5, 2019, No. 10-2019-0103578 filed on Aug. 23, 2019, No.10-2019-0138603 filed on Nov. 1, 2019, and No. 10-2020-0036642 filed onMar. 26, 2020 with the Korean Intellectual Property Office (KIPO), theentire contents of which are hereby incorporated by reference.

BACKGROUND 1. Technical Field

The present disclosure relates to feedback technologies in acommunication system, and more specifically, to techniques fortransmitting or receiving uplink feedback information in a sharedspectrum.

2. Related Art

The communication system (hereinafter, a New Radio (NR) communicationsystem) using a higher frequency band (e.g., a frequency band of 6 GHzor higher) than a frequency band (e.g., a frequency band of 6 GHz orlower) of the Long Term Evolution (LTE) (or, LTE-A) is being consideredfor processing of soaring wireless data. The NR communication system maysupport not only a frequency band below 6 GHz but also 6 GHz or higherfrequency band, and may support various communication services andscenarios as compared to the LTE communication system. For example,usage scenarios of the NR communication system may include enhancedmobile broadband (eMBB), ultra-reliable low-latency communication(URLLC), massive machine type communication (mMTC), and the like.

Meanwhile, one numerology related to an orthogonal frequency divisionmultiplexing (OFDM) waveform may be used in the LTE communicationsystem, and multiple numerologies related to OFDM waveforms may be usedin the NR communication system. A time division duplex (TDD) basedcommunication system may support both the eMBB and the URLLC. In thiscase, a low latency performance of the URLLC needs to be improved. In adownlink communication procedure, transmission of a hybrid automaticrepeat request (HARM) response for downlink data may be required.Therefore, a transmission delay time in the downlink communicationprocedure may be determined based on a repetition periodicity ofdownlink (DL) slot and uplink (UL) slot. In an uplink communicationprocedure, the base station may transmit a UL grant to the terminalthrough a DL slot. Therefore, a transmission delay time in the uplinkcommunication procedure may be determined based on a repetitionperiodicity of DL slot and UL slot.

In the NR communication system, the type of slot may be changeddynamically. The types of slot may be classified into a DL slot, a ULslot, and a flexible (FL) slot. The FL slot may be changed to a DL slotor a UL slot. The terminal may identify the type of the slot in symbolunits. In the LTE communication system, the type of subframe may bechanged. The type of subframe may be classified into a DL subframe, a ULsubframe, and a special subframe.

Meanwhile, in a shared spectrum, the terminal may determine an occupancystate of a channel by performing a listen before talk (LBT) operation,and may transmit uplink feedback information to the base station byusing a channel in an idle state. However, when the occupancy state ofthe channel is in a busy state, the terminal may not transmit uplinkfeedback information. In this case, since transmission delay of theuplink feedback information occurs, methods for solving this problem areneeded.

SUMMARY

Accordingly, exemplary embodiments of the present disclosure provide amethod and an apparatus for transmitting or receiving uplink feedbackinformation in a communication system operating in a shared spectrum.

According to a first exemplary embodiment of the present disclosure, anoperation method of a terminal in a communication system comprisesreceiving downlink control information (DCI) from a base station, theDCI including resource allocation information of a physical downlinkshared channel (PDSCH); receiving data #n from the base station throughthe PDSCH indicated by the DCI; generating a hybrid automatic repeatrequest (HARQ) codebook including an HARQ response bit #n for the data#n and an HARQ response bit #n-1 for data #n-1 received from the basestation before the data #n; and transmitting the HARQ codebook to thebase station, wherein the HARQ response bit #n and the HARQ response bit#n-1 are arranged in the HARQ codebook in an order of HARQ processnumbers, and n is a natural number.

The HARQ codebook may further include a new data indicator (NDI) #nassociated with the HARQ response bit #n and an NDI #n-1 associated withthe HARQ response bit #n-1.

The HARQ response bit #n may be concatenated with the NDI #n, the HARQresponse bit #n-1 may be concatenated with the NDI #n-1, and theconcatenated HARQ response bit #n and NDI #n and the concatenated HARQresponse bit #n-1 and NDI #n-1 may be arranged in the HARQ codebook inthe order of the HARQ process numbers.

The HARQ codebook may include HARQ response bits associated with allHARQ processes configured in the terminal or include the HARQ responsebits generated by concatenating in an order of HARQ process identifiesand NDIs associated with the HARQ response bits.

The DCI may further include a field indicating whether transmission ofthe HARQ codebook is triggered.

The HARQ codebook may be transmitted through a physical uplink controlchannel (PUCCH), and information indicating one or more indices of aresource block (RB) set to which the PUCCH belongs and one or moreinterlace indices of the PUCCH in the RB set may be received from thebase station.

The information indicating the index of the RB set and the interlaceindex may be received from the base station through a radio resourcecontrol (RRC) message.

When a decoding operation for the data #n is not completed, a value ofthe HARQ response bit #n included in the HARQ codebook may be notconfigured to be a HARQ response bit for the data #n.

According to a second exemplary embodiment of the present disclosure, anoperation method of a base station in a communication system comprisestransmitting downlink control information (DCI) to a terminal, the DCIincluding resource allocation information of a physical downlink sharedchannel (PDSCH) #n; transmitting the PDSCH #n through resourcesindicated by the resource allocation information; and receiving a hybridautomatic repeat request (HARQ) codebook including an HARQ response bit#n for the PDSCH #n and an HARQ response bit #n-1 for a PDSCH #n-1,wherein the HARQ response bit #n and the HARQ response bit #n-1 arearranged in the HARQ codebook in an order of the PDSCH #n and the PDSCH#n-1, and n is a natural number.

The PDSCH #n and the PDSCH #n-1 may belong to same PDSCH group.

Each of the PDSCH #n and the PDSCH #n-1 may belong to different PDSCHgroups.

The DCI may further includes a field indicating a number of PDSCH groupsto be feedbacked, the field set as a first value may indicate feedbackof a HARQ response for one PDSCH group, and the field set as a secondvalue may indicate feedback of a HARQ response for a plurality of PDSCHgroups.

The HARQ codebook may be received through a physical uplink controlchannel (PUCCH), and information indicating one or more indices of aresource block (RB) set to which the PUCCH belongs and one or moreinterlace indices of the PUCCH in the RB set may be transmitted to theterminal through higher layer signaling.

According to a third exemplary embodiment of the present disclosure, aterminal in a communication system comprises a processor; and a memoryelectronically communicating with the processor and storing instructionsexecutable by the processor, wherein when executed by the processor, theinstructions cause the terminal to receive downlink control information(DCI) from a base station, the DCI including resource allocationinformation of a physical downlink shared channel (PDSCH); receive data#n from the base station through the PDSCH indicated by the DCI;generate a hybrid automatic repeat request (HARQ) codebook including anHARQ response bit #n for the data #n and an HARQ response bit #n-1 fordata #n-1 received from the base station before the data #n; andtransmit the HARQ codebook to the base station, wherein the HARQresponse bit #n and the HARQ response bit #n-1 are arranged in the HARQcodebook in an order of HARQ process numbers, and n is a natural number.

The HARQ codebook may further include a new data indicator (NDI) #nassociated with the HARQ response bit #n and an NDI #n-1 associated withthe HARQ response bit #n-1.

The HARQ response bit #n may be concatenated with the NDI #n, the HARQresponse bit #n-1 may be concatenated with the NDI #n-1, and theconcatenated HARQ response bit #n and NDI #n and the concatenated HARQresponse bit #n-1 and NDI #n-1 may be arranged in the HARQ codebook inthe order of the HARQ process numbers.

The HARQ codebook may include HARQ response bits associated with allHARQ processes configured in the terminal or include the HARQ responsebits generated by concatenating in an order of HARQ process identifiesand NDIs associated with the HARQ response bits.

The DCI may further includes a field indicating whether transmission ofthe HARQ codebook is triggered.

The HARQ codebook may be transmitted through a physical uplink controlchannel (PUCCH), and information indicating one or more indices of aresource block (RB) set to which the PUCCH belongs and one or moreinterlace indices of the PUCCH in the RB set may be received from thebase station.

When a decoding operation for the data #n is not completed, a value ofthe HARQ response bit #n included in the HARQ codebook may be notconfigured to be a HARQ response bit for the data #n.

According to the exemplary embodiments of the present disclosure, theterminal can transmit a plurality of hybrid automatic repeat request(HARQ) responses to the base station through one physical uplink controlchannel (PUCCH). Here, the plurality of HARQ responses may include anHARQ response for a physical downlink shared channel (PDSCH) scheduledby current downlink control information (DCI) and an HARQ response for aPDSCH scheduled by previous DCI. Therefore, in the communication systemoperating in a shared spectrum, a transmission delay of uplink feedbackinformation can be reduced, and the performance of the communicationsystem can be improved.

BRIEF DESCRIPTION OF DRAWINGS

Exemplary embodiments of the present disclosure will become moreapparent by describing in detail embodiments of the present disclosurewith reference to the accompanying drawings, in which:

FIG. 1 is a conceptual diagram illustrating a first exemplary embodimentof a communication system;

FIG. 2 is a block diagram illustrating a first exemplary embodiment of acommunication node constituting a communication system;

FIG. 3A is a conceptual diagram illustrating a first exemplaryembodiment of a method for arranging an UL control channel in acommunication system;

FIG. 3B is a conceptual diagram illustrating a second exemplaryembodiment of a method for arranging an UL control channel in acommunication system;

FIG. 4A is a sequence chart illustrating a first exemplary embodiment ofan initial access procedure in a communication system;

FIG. 4B is a sequence chart illustrating a second exemplary embodimentof an initial access procedure in a communication system;

FIG. 5 is a conceptual diagram illustrating a first exemplary embodimentof an RAR in a communication system; and

FIG. 6 is a conceptual diagram illustrating a first exemplary embodimentof an UL grant included in an RAR in a communication system.

It should be understood that the above-referenced drawings are notnecessarily to scale, presenting a somewhat simplified representation ofvarious preferred features illustrative of the basic principles of thedisclosure. The specific design features of the present disclosure,including, for example, specific dimensions, orientations, locations,and shapes, will be determined in part by the particular intendedapplication and use environment.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Embodiments of the present disclosure are disclosed herein. However,specific structural and functional details disclosed herein are merelyrepresentative for purposes of describing embodiments of the presentdisclosure. Thus, embodiments of the present disclosure may be embodiedin many alternate forms and should not be construed as limited toembodiments of the present disclosure set forth herein.

Accordingly, while the present disclosure is capable of variousmodifications and alternative forms, specific embodiments thereof areshown by way of example in the drawings and will herein be described indetail. It should be understood, however, that there is no intent tolimit the present disclosure to the particular forms disclosed, but onthe contrary, the present disclosure is to cover all modifications,equivalents, and alternatives falling within the spirit and scope of thepresent disclosure. Like numbers refer to like elements throughout thedescription of the figures.

It will be understood that, although the terms first, second, etc. maybe used herein to describe various elements, these elements should notbe limited by these terms. These terms are only used to distinguish oneelement from another. For example, a first element could be termed asecond element, and, similarly, a second element could be termed a firstelement, without departing from the scope of the present disclosure. Asused herein, the term “and/or” includes any and all combinations of oneor more of the associated listed items.

It will be understood that when an element is referred to as being“connected” or “coupled” to another element, it can be directlyconnected or coupled to the other element or intervening elements may bepresent. In contrast, when an element is referred to as being “directlyconnected” or “directly coupled” to another element, there are nointervening elements present. Other words used to describe therelationship between elements should be interpreted in a like fashion(i.e., “between” versus “directly between,” “adjacent” versus “directlyadjacent,” etc.).

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of the presentdisclosure. As used herein, the singular forms “a,” “an” and “the” areintended to include the plural forms as well, unless the context clearlyindicates otherwise. It will be further understood that the terms“comprises,” “comprising,” “includes” and/or “including,” when usedherein, specify the presence of stated features, integers, steps,operations, elements, and/or components, but do not preclude thepresence or addition of one or more other features, integers, steps,operations, elements, components, and/or groups thereof.

Unless otherwise defined, all terms (including technical and scientificterms) used herein have the same meaning as commonly understood by oneof ordinary skill in the art to which this present disclosure belongs.It will be further understood that terms, such as those defined incommonly used dictionaries, should be interpreted as having a meaningthat is consistent with their meaning in the context of the relevant artand will not be interpreted in an idealized or overly formal senseunless expressly so defined herein.

Hereinafter, exemplary embodiments of the present disclosure will bedescribed in greater detail with reference to the accompanying drawings.In order to facilitate general understanding in describing the presentdisclosure, the same components in the drawings are denoted with thesame reference signs, and repeated description thereof will be omitted.

A communication system to which exemplary embodiments according to thepresent disclosure are applied will be described. The communicationsystem to which the exemplary embodiments according to the presentdisclosure are applied is not limited to the contents described below,and the exemplary embodiments according to the present disclosure may beapplied to various communication systems. Here, the communication systemmay be used in the same sense as a communication network.

FIG. 1 is a conceptual diagram illustrating a first exemplary embodimentof a communication system.

Referring to FIG. 1 , a communication system 100 may comprise aplurality of communication nodes 110-1, 110-2, 110-3, 120-1, 120-2,130-1, 130-2, 130-3, 130-4, 130-5, and 130-6. The plurality ofcommunication nodes may support 4G communication (e.g., long termevolution (LTE) or LTE-Advanced (LTE-A)), 5G communication (e.g., newradio (NR)), or the like as defined in the 3rd generation partnershipproject (3GPP) technical specification. The 4G communication may beperformed in a frequency band of 6 GHz or below, and the 5Gcommunication may be performed in a frequency band of 6 GHz or above aswell as the frequency band of 6 GHz or below.

For example, for the 4G and 5G communications, the plurality ofcommunication nodes may support code division multiple access (CDMA)based communication protocol, wideband CDMA (WCDMA) based communicationprotocol, time division multiple access (TDMA) based communicationprotocol, frequency division multiple access (FDMA) based communicationprotocol, orthogonal frequency division multiplexing (OFDM) basedcommunication protocol, filtered OFDM based communication protocol,cyclic prefix OFDM (CP-OFDM) based communication protocol, discreteFourier transform-spread-OFDM (DFT-s-OFDM) based communication protocol,orthogonal frequency division multiple access (OFDMA) basedcommunication protocol, single carrier FDMA (SC-FDMA) basedcommunication protocol, non-orthogonal multiple access (NOMA) basedcommunication protocol, generalized frequency division multiplexing(GFDM) based communication protocol, filter band multi-carrier (FBMC)based communication protocol, universal filtered multi-carrier (UFMC)based communication protocol, space division multiple access (SDMA)based communication protocol, and the like.

In addition, the communication system 100 may further include a corenetwork. When the communication system 100 supports 4G communication,the core network may include a serving-gateway (S-GW), a packet datanetwork (PDN) gateway (P-GW), a mobility management entity (MME), andthe like. When the communication system 100 supports 5G communication,the core network may include a user plane function (UPF), a sessionmanagement function (SMF), an access and mobility management function(AMF), and the like.

Meanwhile, each of the plurality of communication nodes 110-1, 110-2,110-3, 120-1, 120-2, 130-1, 130-2, 130-3, 130-4, 130-5, and 130-6constituting the communication system 100 may have the followingstructure.

FIG. 2 is a block diagram illustrating a first exemplary embodiment of acommunication node constituting a communication system.

Referring to FIG. 2 , a communication node 200 may comprise at least oneprocessor 210, a memory 220, and a transceiver 230 connected to thenetwork for performing communications. Also, the communication node 200may further comprise an input interface device 240, an output interfacedevice 250, a storage device 260, and the like. Each component includedin the communication node 200 may communicate with each other asconnected through a bus 270.

However, the respective components included in the communication node200 may be connected through a separate interface or a separate busaround the processor 210 instead of the common bus 270. For example, theprocessor 210 may be connected to at least one of the memory 220, thetransceiver 230, the input interface device 240, the output interfacedevice 250, and the storage device 260 through a dedicated interface.

The processor 210 may execute a program stored in at least one of thememory 220 and the storage device 260. The processor 210 may refer to acentral processing unit (CPU), a graphics processing unit (GPU), or adedicated processor on which methods in accordance with embodiments ofthe present disclosure are performed. Each of the memory 220 and thestorage device 260 may be constituted by at least one of a volatilestorage medium and a non-volatile storage medium. For example, thememory 220 may comprise at least one of read-only memory (ROM) andrandom access memory (RAM).

Referring again to FIG. 1 , the communication system 100 may comprise aplurality of base stations 110-1, 110-2, 110-3, 120-1, and 120-2, and aplurality of terminals 130-1, 130-2, 130-3, 130-4, 130-5, and 130-6. Thecommunication system 100 including the base stations 110-1, 110-2,110-3, 120-1, and 120-2 and the terminals 130-1, 130-2, 130-3, 130-4,130-5, and 130-6 may be referred to as an ‘access network’. Each of thefirst base station 110-1, the second base station 110-2, and the thirdbase station 110-3 may form a macro cell, and each of the fourth basestation 120-1 and the fifth base station 120-2 may form a small cell.The fourth base station 120-1, the third terminal 130-3, and the fourthterminal 130-4 may belong to the cell coverage of the first base station110-1. Also, the second terminal 130-2, the fourth terminal 130-4, andthe fifth terminal 130-5 may belong to the cell coverage of the secondbase station 110-2. Also, the fifth base station 120-2, the fourthterminal 130-4, the fifth terminal 130-5, and the sixth terminal 130-6may belong to the cell coverage of the third base station 110-3. Also,the first terminal 130-1 may belong to the cell coverage of the fourthbase station 120-1, and the sixth terminal 130-6 may belong to the cellcoverage of the fifth base station 120-2.

Here, each of the plurality of base stations 110-1, 110-2, 110-3, 120-1,and 120-2 may be referred to as NodeB (NB), evolved NodeB (eNB), gNB,advanced base station (ABS), high reliability-base station (HR-BS), basetransceiver station (BTS), radio base station, radio transceiver, accesspoint (AP), access node, radio access station (RAS), mobile multihoprelay-base station (MMR-BS), relay station (RS), advanced relay station(ARS), high reliability-relay station (HR-RS), home NodeB (HNB), homeeNodeB (HeNB), road side unit (RSU), radio remote head (RRH),transmission point (TP), transmission and reception point (TRP), or thelike. Each of the plurality of terminals 130-1, 130-2, 130-3, 130-4,130-5, and 130-6 may be referred to as user equipment (UE), terminalequipment (TE), advanced mobile station (AMS), high reliability-mobilestation (HR-MS), terminal, access terminal, mobile terminal, station,subscriber station, mobile station, portable subscriber station, node,device, on board unit (OBU), or the like.

Meanwhile, each of the plurality of base stations 110-1, 110-2, 110-3,120-1, and 120-2 may operate in the same frequency band or in differentfrequency bands. The plurality of base stations 110-1, 110-2, 110-3,120-1, and 120-2 may be connected to each other via an ideal backhaullink or a non-ideal backhaul link, and exchange information with eachother via the ideal or non-ideal backhaul. Also, each of the pluralityof base stations 110-1, 110-2, 110-3, 120-1, and 120-2 may be connectedto the core network through the ideal backhaul link or non-idealbackhaul link. Each of the plurality of base stations 110-1, 110-2,110-3, 120-1, and 120-2 may transmit a signal received from the corenetwork to the corresponding terminal 130-1, 130-2, 130-3, 130-4, 130-5,or 130-6, and transmit a signal received from the corresponding terminal130-1, 130-2, 130-3, 130-4, 130-5, or 130-6 to the core network.

Also, each of the plurality of base stations 110-1, 110-2, 110-3, 120-1,and 120-2 may support a multi-input multi-output (MIMO) transmission(e.g., single-user MIMO (SU-MIMO), multi-user MIMO (MU-MIMO), massiveMIMO, or the like), a coordinated multipoint (CoMP) transmission, acarrier aggregation (CA) transmission, a transmission in a sharedspectrum, a device-to-device (D2D) communication (or, proximity services(ProSe)), an Internet of Things (IoT) communication, a dual connectivity(DC), or the like. Here, each of the plurality of terminals 130-1,130-2, 130-3, 130-4, 130-5, and 130-6 may perform operationscorresponding to the operations of the plurality of base stations 110-1,110-2, 110-3, 120-1, and 120-2 (i.e., the operations supported by theplurality of base stations 110-1, 110-2, 110-3, 120-1, and 120-2). Forexample, the second base station 110-2 may transmit a signal to thefourth terminal 130-4 in the SU-MIMO manner, and the fourth terminal130-4 may receive the signal from the second base station 110-2 in theSU-MIMO manner. Alternatively, the second base station 110-2 maytransmit a signal to the fourth terminal 130-4 and fifth terminal 130-5in the MU-MIMO manner, and the fourth terminal 130-4 and fifth terminal130-5 may receive the signal from the second base station 110-2 in theMU-MIMO manner.

Each of the first base station 110-1, the second base station 110-2, andthe third base station 110-3 may transmit a signal to the fourthterminal 130-4 in the CoMP transmission manner, and the fourth terminal130-4 may receive the signal from the first base station 110-1, thesecond base station 110-2, and the third base station 110-3 in the CoMPmanner. Also, each of the plurality of base stations 110-1, 110-2,110-3, 120-1, and 120-2 may exchange signals with the correspondingterminals 130-1, 130-2, 130-3, 130-4, 130-5, or 130-6 which belongs toits cell coverage in the CA manner. Each of the base stations 110-1,110-2, and 110-3 may control D2D communications between the fourthterminal 130-4 and the fifth terminal 130-5, and thus the fourthterminal 130-4 and the fifth terminal 130-5 may perform the D2Dcommunications under control of the second base station 110-2 and thethird base station 110-3.

Hereinafter, methods for transmitting or receiving uplink feedbackinformation in a communication system will be described. Even when amethod (e.g., transmission or reception of a signal) to be performed ata first communication node among communication nodes is described, acorresponding second communication node may perform a method (e.g.,reception or transmission of the signal) corresponding to the methodperformed at the first communication node. That is, when an operation ofa terminal is described, a corresponding base station may perform anoperation corresponding to the operation of the terminal. Conversely,when an operation of the base station is described, the correspondingterminal may perform an operation corresponding to the operation of thebase station.

The terminal may receive a physical downlink shared channel (PDSCH) fromthe base station, and may transmit a hybrid automatic repeat request(HARQ) response (e.g., acknowledgment (ACK) or negative ACK (NACK)) forthe PDSCH to the base station. The HARQ response may be ‘HARQ-ACK’ or‘HARQ-ACK bit’ defined in the technical specification. Alternatively,the HARQ response may mean a HARQ codebook which is generated based onthe HARQ-ACK bit. When the HARQ response received from the terminal isNACK, the base station may retransmit the same transport block (TB).When the HARQ response received from the terminal is ACK, the basestation may perform operations for transmission of another TB.

Radio resources used for transmission of the HARQ response may beconfigured by the base station. For example, the base station maytransmit resource configuration information for uplink feedback to theterminal, and the terminal may transmit an HARQ response to the basestation using radio resources indicated by the resource configurationinformation. A method for configuring the resources for uplink feedbackmay vary according to an operation state of the terminal. The firstoperation state of the terminal may correspond to a case when theterminal that has not established a radio resource control (RRC)connection with the base station performs an initial access procedure(e.g., a cell search procedure or a random access procedure) or a casewhen the terminal transmits an HARQ response for a PDSCH in an RRCconnection reconfiguration procedure. The second operation state of theterminal may correspond to a case when the terminal operating in an RRCconnected state transmits an HARQ response for a PDSCH.

In the first operation state of the terminal, because the RRC connectionbetween the terminal and the base station is not established (e.g.,because a specific RRC connection between the terminal and the basestation is not assumed), the base station may transmit resourceconfiguration information for uplink feedback to unspecified terminalsby using higher layer signaling. In addition, the base station mayinform a terminal of a radio resource(s) of a UL control channel to beused by the terminal among the radio resources configured by the higherlayer signaling through physical layer signaling.

In the second operation state of the terminal, the base station mayinform the corresponding terminal of radio resources of a UL controlchannel available for the terminal by using higher layer signaling inthe RRC connection configuration procedure. In addition, the basestation may inform the corresponding terminal of a radio resource(s) ofa UL control channel to be used by the terminal among the radioresources configured by the higher layer signaling through physicallayer signaling.

Here, the higher layer signaling may mean a procedure of transmittingand receiving an RRC message, medium access control (MAC) layersignaling may mean a procedure of transmitting and receiving a MACcontrol element (CE), and the physical layer signaling may be aprocedure of transmitting and receiving a physical downlink controlchannel (PDCCH) (e.g., downlink control information (DCI)). In thefollowing exemplary embodiments, a channel (e.g., PDCCH, PDSCH, PUCCH,PUSCH, PSCCH, PS SCH, etc.) may mean ‘signal including data and/orcontrol information’ or ‘radio resource through which data and/orcontrol information is transmitted’. In addition, the signal may be aconcept including a channel and a reference signal.

In order to comply with the frequency regulation (e.g., spectrumregulation) in the communication system operating in an unlicensed band,a UL control channel may occupy many frequency resources. Within abandwidth, one UL control channel may occupy physical resource blocks(PRBs) having a regular interval in the frequency domain.

FIG. 3A is a conceptual diagram illustrating a first exemplaryembodiment of a method for arranging an UL control channel in acommunication system, and FIG. 3B is a conceptual diagram illustrating asecond exemplary embodiment of a method for arranging an UL controlchannel in a communication system.

Referring to FIGS. 3A and 3B, a bandwidth of a communication system maybe 20 MHz, and a subcarrier spacing thereof may be 30 kHz. In this case,the frequency band may consist of 51 PRBs. The UL control channel may bearranged every five PRBs. The arrangement structure of the UL controlchannel may be an interlace structure. In the exemplary embodiment shownin FIG. 3A, one UL control channel may occupy one PRB in the frequencydomain and two symbols in the time domain. In the exemplary embodimentshown in FIG. 3B, one UL control channel may occupy one PRB in thefrequency domain and four symbols in the time domain.

The UL control channel may include a demodulation-reference signal(DM-RS) resource. The DM-RS resource may be time-division multiplexed(TDMed) or frequency-division-multiplexed (FDMed) with uplink controlinformation (UCI) resources. Five interlaces may be defined in theentire band of the communication system. Each interlace may have 10 PRBsor 11 PRBs. When the bandwidth of the communication system is 20 MHz andthe subcarrier spacing thereof is a value (e.g., 15 kHz, 60 kHz, 120kHz, 240 kHz, etc.) other than 30 kHz, the number of PRBs constitutingeach interlace may be different from the number of PRBs in theabove-described exemplary embodiment.

Meanwhile, the base station may transmit a discovery signal and systeminformation. The discovery signal may be a discovery reference signal(DRS) composed of a SS/PBCH block consisting of a primarysynchronization signal (PSS), a secondary synchronization signal (SSS),and a physical broadcast channel (PBCH), or ‘SS/PBCH block and areference signal (e.g., channel state information-reference signal(CSI-RS), etc.)’. When the communication system operates in a licensedband, the base station may periodically transmit the discovery signal.On the other hand, when the communication system operates in anunlicensed band, the base station may transmit the discovery signalaperiodically. The base station may transmit system information througha PDSCH, and may transmit information for decoding the systeminformation through a PDCCH. The terminal may recognize the presence ofthe base station by receiving the discovery signal, derive a resourceposition of the PDSCH based on information obtained from the PDCCH(e.g., information elements included in the DCI), and decode the systeminformation included in the PDSCH. The system information may includeresource allocation information of a physical random access channel(PRACH). The terminal may establish an RRC connection with the basestation by performing an initial access procedure using the PRACHindicated by the resource allocation information included in the systeminformation.

FIG. 4A is a sequence chart illustrating a first exemplary embodiment ofan initial access procedure in a communication system, and FIG. 4B is asequence chart illustrating a second exemplary embodiment of an initialaccess procedure in a communication system.

Referring to FIGS. 4A and 4B, the base station may transmit a discoverysignal (e.g., SS/PBCH block or DRS block) and system information to theterminal (S401). The terminal may receive the discovery signal and thesystem information from the base station, and may identify resourceallocation information of a PRACH included in the system information.The terminal may transmit a random access (RA) preamble (e.g., MSG1) tothe base station through the PRACH indicated by the resource allocationinformation (S402).

The base station may receive RA preamble(s) from unspecifiedterminal(s), and may transmit a random access response (RAR) message(e.g., MSG2) for the RA preamble through a PDSCH (S403). The RAR mayinclude an index of the RA preamble detected at the base station. Inaddition, in the step S403, DCI including scheduling information of thePDSCH through which the RAR is transmitted and/or uplink resourceallocation information (e.g., UL grant) may be transmitted from the basestation to the terminal. Here, the UL grant may be included in the RAR.In the exemplary embodiments, DCI including a DL grant may be referredto as ‘DL-DCI’ and DCI including a UL grant may be referred to as‘UL-DCI’.

The terminal may receive the RAR from the base station, and may comparean index of the RA preamble included in the RAR with an index of the RApreamble transmitted by the terminal in the step S402. When the index ofthe RA preamble included in the RAR is different from the index of theRA preamble transmitted by the terminal in the step S402, the terminalmay perform the step S402 again. When the index of the RA preambleincluded in the RAR is the same as the index of the RA preambletransmitted by the terminal in the step S402, the terminal may transmita MSG3 through a PUSCH indicated by the UL grant received in the stepS403 (S404). The MSG3 may be an RRC connection request message. Theterminal may perform an encoding operation on the RRC connection requestmessage, and may map the encoded RRC connection request message to thePUSCH.

The base station may receive the MSG3 (e.g., RRC connection requestmessage) from the terminal. The base station may transmit a MSG4 to theterminal through a PDSCH (S405-1, S405-2). The MSG4 may be an RRCconnection setup message, and the RRC connection setup message mayinclude a terminal identifier (e.g., cell-radio network temporaryidentifier (C-RNTI)). In the step S405-1 shown in FIG. 4A, DCI includingscheduling information of the PDSCH through which the MSG4 istransmitted may be transmitted from the base station to the terminal. Inthe step S405-2 shown in FIG. 4B, the DCI and a UL grant includingscheduling information of the PDSCH through which the MSG4 istransmitted may be transmitted from the base station to the terminal.The terminal may receive the MSG4 from the base station, and maydetermine whether a contention (e.g., collision) has been resolved basedon the terminal identifier included in the MSG4.

In a step S406-1 shown in FIG. 4A, when the MSG4 is successfullyreceived in the step S405-1, the terminal may transmit ACK for the MSG4to the base station through a PUSCH. The HARQ response (e.g., ACK) maybe a MSG5. The PUSCH through which the ACK is transmitted may beindicated by the UL grant received in the step S405-1. On the otherhand, when the MSG4 is not successfully received in the step S405-1(e.g., when NACK for the MSG4 occurs), the terminal may not performsubsequent procedures. In this case, the terminal may not transmit NACKfor the MSG4 to the base station through the PUSCH. Alternatively, inthe step S406-1, the terminal may transmit NACK for the MSG4 to the basestation through the PUSCH.

When ACK for the MSG4 is received from the terminal, the base stationmay determine that the MSG4 has been successfully received at theterminal. When the HARQ response for the MSG4 is not received from theterminal within a preconfigure time duration or when NACK for the MSG4is received, the base station may determine that MSG4 has not beenreceived at the terminal. That is, the base station may determine thatthe collision of the MSG4 has occurred. When the MSG4 is not received,the terminal may expect to receive the MSG4 from the base station again.When a collision is detected in an identification procedure of theterminal identifier (e.g., C-RNTI, temporary C-RNTI (i.e., TC-RNTI)),the terminal may perform the initial access procedure again.

When there is no terminal that has transmitted the MSG5 in step S406-1,the base station may not distinguish between a case when the decodingoperation of the MSG4 has failed in the terminal and a case when MSG5sof terminals collide. In this case, the base station may retransmit theMSG4 within a specific time window to establish the RRC connection withthe terminal. Alternatively, the base station may not perform theretransmission procedure of the MSG4. When the MSG4 is notretransmitted, the time window may be unnecessary.

Meanwhile, in the step S406-2 shown in FIG. 4B, the terminal maytransmit the HARQ response (e.g., ACK or NACK) for the MSG4 to theterminal through a PUCCH. The PUCCH through which the HARQ response forthe MSG4 is transmitted may be configured in the terminal in the initialaccess procedure. The base station may receive the HARQ response fromthe terminal, and may determine whether the MSG4 has been successfullyreceived at the terminal based on the HARQ response. The base stationmay transmit DCI (e.g., UL-DCI) including a UL grant to the terminal(S407). The terminal may receive the DCI from the base station, and maytransmit the MSG5 to the base station using a PUSCH indicated by the ULgrant included in the DCI (S408). The base station may receive the MSG5from the terminal.

Energy Detection Threshold

An energy detection threshold used for a listen-before-talk (LBT)operation may be indicated by information included in the UL grantbelonging to the RAR or information other than the UL grant. Theterminal performing the LBT operation may compare an energy detectionresult with the energy detection threshold in sensing slot(s) belongingto a defer duration. When the energy detection result is less than theenergy detection threshold, the terminal may determine that the sensingslot(s) are in an idle state. When the energy detection result isgreater than or equal to the energy detection threshold, the terminalmay determine that the corresponding sensing slot(s) are in a busystate. Here, the sensing slot may have a length of 9 μs.

The sensing slot may be distinguished from a slot used for transmittingdata and/or control information. An energy detection threshold offsetmay be used instead of the energy detection threshold. The energydetection threshold may be ‘maxEnergyDetectionThreshold’ defined in thetechnical specification, and the energy detection threshold offset maybe ‘energyDetectionThresholdOffset’ defined in the technicalspecification. The terminal may derive the energy detection threshold indB units based on the contents defined in the section 4.2.3 of the 3GPPtechnical specification (TS) 37.213.

Remaining Minimum System Information (RMSI) in a Communication SystemOperating in an Unlicensed Band

The terminal may synchronize with the base station by receiving thediscovery signal (e.g., SS/PBCH block or DRS block) from the basestation, and may obtain configuration information of a CORESET 0 (orType0-PDCCH common search space) from a PBCH of the discovery signal.The terminal may perform a PDCCH monitoring operation in a search space0 within the CORESET 0, and obtain a system information block 1 (SIB1)(e.g., RMSI) in a PDSCH-1_0 indicated by DCI obtained by the PDCCHmonitoring operation. The terminal may obtain configuration informationfor an initial access procedure from the SIB1. The RMSI (e.g., SIB1) mayinclude one or more of the following information elements (PRACHconfiguration information, energy detection threshold, PUCCHconfiguration information, common radio identifier).

PRACH Configuration Information

The RMSI may include PRACH configuration information. The PRACHconfiguration information may include time resource information andfrequency resource information of a PRACH through which a RA preamble istransmitted. In addition, information indicating a subcarrier spacingused for transmission of the RA preamble may be included in the RMSI.

Energy Detection Threshold

The RMSI may include the energy detection threshold. The terminal mayperform an LBT operation to transmit the RA preamble. In this case, theterminal may transmit the RA preamble when all sensing slots belongingto a defer duration are determined to be in the idle state. The terminalmay detect an energy of a received signal in each sensing slot (or aportion of each sensing slot) belonging to the defer duration, and whenthe energy detection result is less than the energy detection threshold,the terminal may determine that the corresponding sensing slot is in theidle state. On the other hand, when the energy detection result isgreater than or equal to the energy detection threshold, the terminalmay determine that the corresponding sensing slot is in the busy state.The energy detection threshold may be used to determine whether or notit is possible to access the corresponding channel.

As described above, the energy detection threshold offset may be usedinstead of the energy detection threshold. The energy detectionthreshold may be ‘maxEnergyDetectionThreshold’ defined in the technicalspecification, and the energy detection threshold offset may be‘energyDetectionThresholdOffset’ defined in the technical specification.The terminal may derive the energy detection threshold in dB units basedon the contents defined in the section 4.2.3 of the 3GPP technicalspecification (TS) 37.213.

PUCCH Configuration Information

The RMSI may include PUCCH configuration information. The PUCCHconfiguration information may include time resource information andfrequency resource information of the PUCCH through which the HARQresponse is transmitted in the initial access procedure. The PUCCHconfiguration information may be included in the UL grant.

Common Radio Identifier (e.g., RNTI)

The RMSI may include a radio identifier (e.g., common radio identifier).The terminal(s) may transmit a PUSCH according to a trigger scheme. Whenthe terminal transmits a PUSCH according to the trigger scheme within atime duration (e.g., channel occupancy time (COT)) secured by the basestation, the LBT operation may be simplified, and orthogonality betweenPUSCHs transmitted by a plurality of terminals can be ensured at thebase station.

The first PUSCH transmitted by the terminal in the initial accessprocedure may be the MSG3, and the MSG3 may be the HARQ response to theRAR. The common RNTI may be included in the RAR instead of the RMSI. Theinformation obtained through the RMSI may be used in the initial accessprocedure or the RRC connection reconfiguration procedure. Until an HARQresponse (e.g., ACK) for an RRC message is received from the terminal inthe RRC connection reconfiguration procedure, the base station may notknow how the corresponding RRC message is reflected in the terminal. Inthis reason, it may be preferable to use information that the terminalcan obtain in the RRC idle state. Therefore, it may be preferable forthe common RNTI to be included in the RMSI. On the other hand, wheninformation other than the common RNTI is exchanged through the RRCmessages in the RRC connection reconfiguration procedure, the commonRNTI may not be included in the RMSI.

RAR in a Communication System Operating in an Unlicensed Band

When the base station operates in a licensed band, the RAR may beconfigured in units of bytes. For example, the size of the RAR may be nbytes. Here, n may be a natural number.

FIG. 5 is a conceptual diagram illustrating a first exemplary embodimentof an RAR in a communication system, and FIG. 6 is a conceptual diagramillustrating a first exemplary embodiment of an UL grant included in anRAR in a communication system.

Referring to FIG. 5 , an RAR (e.g., MAC RAR) may include a timingadvance (TA) command, a UL grant, and information on a temporaryidentifier (e.g., a temporary C-RNTI (TC-RNTI)). The MAC layer of theterminal may generate the RAR, the RAR may be encoded, and the encodedRAR may be mapped to a PUSCH.

Referring to FIG. 6 , the UL grant included in the RAR may include afrequency hopping flag, PUSCH frequency resource allocation information,PUSCH time resource allocation information, modulation and coding scheme(MCS) information, transmission power control (TPC) command for a PUSCH,and CSI request information. On the other hand, in the communicationsystem operating in an unlicensed band, the UL grant included in the RARmay include one or more information elements and additional informationelement(s) shown in FIG. 6 . New field(s) may be introduced to the ULgrant for the additional information element(s). Existing fieldsincluded in the UL grant may be unnecessary.

UL Grant Included in RAR

The UL grant may include one or more of the following informationelements. Since the UL grant is included in a MAC message, all thefields constituting the UL grant may be configured in units of bytes. Tosupport this operation, specific bit(s) in the fields may be configuredas reserved bits. Alternatively, the specific bit(s) may be set to apredefined value (e.g., ‘0’ or ‘1’). The terminal may generate acodeword by performing an encoding operation on the UL grant, and maymap the codeword to a PUSCH.

Trigger Field

The UL grant belonging to the RAR may include a trigger field. Thenumber of trigger fields included in the UL grant may vary depending onthe triggering scheme of a PUSCH. One trigger field (e.g., trigger Afield) or two trigger fields (e.g., trigger A field and trigger B field)may be needed for triggering PUSCH transmission. The trigger A field andthe trigger B field may be included in different UL grants (or differentPDCCHs).

The trigger A field included in the UL grant may indicate two differentvalues. The terminal may determine whether to perform a monitoringoperation on the trigger B field according to the value indicated by thetrigger A field. The trigger A field set to a first value (e.g., ‘0’)may indicate a non-trigger scheme. In this case, the terminal maytransmit the PUSCH based on the UL grant. For example, the terminal mayidentify a slot in which the LBT operation for PUSCH transmission startsbased on a slot offset field included in the UL grant. The trigger Afield set to a second value (e.g., ‘1’) may indicate a triggeringscheme. In this case, the terminal may receive an additional PDCCH thattriggers PUSCH transmission. The additional PDCCH may include thetrigger B field. The terminal may identify the slot in which the LBToperation for PUSCH transmission starts based on the informationelement(s) (e.g., trigger B field) included in the additional PDCCH.

Common RNTI

The RAR (e.g., UL grant belonging to the RAR) may include a radioidentifier (e.g., common RNTI). The terminal(s) may transmit a PUSCHaccording to the trigger scheme. When the terminal transmits a PUSCHaccording to the trigger scheme within a time duration (e.g., COT)secured by the base station, the LBT operation may be simplified, andorthogonality between PUSCHs transmitted by a plurality of terminals maybe ensured at the base station.

The terminal may generate a PUSCH using the UL grant belonging to theRAR to transmit the MSG3. A method of indicating a transmission timepoint of the PUSCH may vary according to the value of the trigger fieldincluded in the UL grant. For example, the UL grant (e.g., the UL grantbelonging to the RAR) may include information indicating thetransmission time point of the PUSCH. Alternatively, an additional ULgrant scrambled by a common RNTI may include information indicating thetransmission time point of the PUSCH.

The UL grant (e.g., common DCI) addressed by the common RNTI may betransmitted to unspecified terminal(s) and may not include PUSCHresource allocation information. The common DCI may play a role (e.g., atrigger role) of indicating a slot in which the PUSCH can betransmitted.

Slot Offset Field

The UL grant belonging to the RAR may include a slot offset field. Theterminal may identify a slot in which the LBT operation for PUSCHtransmission starts based on a time offset indicated by the slot offsetfield. The time offset(s) may be defined in the technical specification.The base station may transmit to the terminal the UL grant including theslot offset field indicating an index of one time offset among the timeoffset(s) defined in the technical specification.

When the RAR does not include the trigger field, when the trigger fieldis not configured to the terminal through higher layer signaling, orwhen the trigger A field is set to the first value, the terminal maydetermine the slot in which the LBT operation for PUSCH transmissionstarts by applying the time offset from the slot in which the RAR isreceived. When the trigger A field is set to the second value, theterminal may determine the slot in which the LBT operation for PUSCHtransmission starts by applying the time offset from the slot in whichthe trigger B field is received. The trigger B field may be included inthe common DCI.

Start Symbol and Length Field

The UL grant belonging to the RAR may include a start symbol and lengthfield. The start symbol and length field may express the start symbol ofthe PUSCH or the start symbol and the end symbol of the PUSCH as oneindex. The terminal may identify the start symbol of the PUSCH and thenumber of symbols belonging to the PUSCH based on the index indicated bythe start symbol and length field. The PUSCH may be configured based ona type A mapping scheme or a type B mapping scheme.

Start Time Point Field

The UL grant belonging to the RAR may include a start time point field,and the start time point field may indicate a start time point of thePUSCH. The transmission of the

PUSCH may start at a slot boundary. Alternatively, considering a timeand/or a TA required for the LBT operation, the transmission of thePUSCH may be started at a time point not a symbol boundary. Thetransmission of the PUSCH may start at a symbol j, a symbol j+1, or atime point between the symbol j and the symbol j+1. Alternatively, thetransmission of the PUSCH may start at a time point after apreconfigured time (e.g., 25 μs or 16 μs) from the start of the symbol jor at a time point after a (preconfigured time (e.g., 25 μs or 16μs)+TA) from the start of the symbol j. In this case, the transmissionof the PUSCH may be performed by extending a cyclic prefix (CP) of thesymbol j+1. According to this operation, a phase of a waveform of thesymbol may be continuously expressed, and a peak to average power ratio(PAPR) of the symbol j+1 may be reduced. The slot and the start symbolin which the PUSCH is transmitted may be indicated by the RAR (e.g., ULgrant belonging to the RAR). In addition, the transmission time point ofthe PUSCH within the start symbol may be indicated by the RAR (e.g., ULgrant belonging to the RAR).

Frequency Resource Field

The UL grant belonging to the RAR may include a frequency resourcefield, and the frequency resource field may indicate a frequencyresource of the PUSCH. The frequency resource of the PUSCH may beindicated by one or more interlace indexes. The terminal may identifyPRB(s) in which the PUSCH is transmitted based on the interlace indexindicated by the frequency resource field. Only a small number of bitsmay be needed to express all interlaces. Therefore, the frequencyresource field included in the UL grant may consist of only a smallnumber of bits.

The transmission operation of the PUSCH (e.g., PUSCH including the MSG3)that is a response to the RAR may be performed in one LBT subband. TheLBT subband may mean a resource block (RB) set. The base station maytransmit information indicating that the transmission operation of thePUSCH is performed in a licensed carrier (e.g., supplementary uplink(SUL) carrier) or an unlicensed carrier to the terminal. Here, thelicensed carrier may mean a carrier located in a licensed band, and theunlicensed carrier may mean a carrier located in an unlicensed band. Thecarrier in which the RA preamble is transmitted may be the same as thecarrier in which the PUSCH including the MSG3 is transmitted.Alternatively, the carrier in which the RA preamble is transmitted maybe different from the carrier in which the PUSCH including the MSG3 istransmitted.

When the terminal transmits the RA preamble and the MSG3 (e.g., PUSCHincluding the MSG3) in a licensed carrier, the conventional initialaccess procedure may be performed. When the RA preamble is transmittedin an unlicensed carrier and the MSG3 (e.g., PUSCH including the MSG3)is transmitted in a licensed carrier, the UL grant belonging to the RARmay include a field indicating the licensed carrier (e.g., licensedband) in which the MSG3 is transmitted. For example, the UL grant mayinclude a carrier field indicating a carrier index. The carrierindicated by the carrier field included in the UL grant may be thecarrier (e.g., licensed carrier or unlicensed carrier) used for thetransmission of the MSG3.

In a proposed method, the RAR may be mapped to one interlace. Therefore,the UL grant belonging to the RAR may include one interlace index. TheUL grant scheduling the PUSCH may include one or more interlace indexes.In this case, the UL grant may include a bitmap or a code pointindicating a combination of one or more interlace indexes. Each bitincluded in the bitmap may correspond to one interlace index. When thecode point is used, the size of the frequency resource field included inthe UL grant may be reduced.

In another proposed method, the RAR may be mapped to up to apredetermined number of interlace(s). The UL grant belonging to the RARmay include a bitmap or a code point indicating one or more interlaceindexes. The maximum number of interlaces to which the MSG3 (e.g., PUSCHincluding the MSG3) is mapped may be limited. The maximum number ofinterlaces for the MSG3 may be defined in the technical specification.Alternatively, the base station may transmit information indicating themaximum number of interlaces for the MSG3 to the terminal using higherlayer signaling.

Channel Access Information Field

The UL grant belonging to the RAR may include a channel accessinformation field. The channel access field may indicate the type of LBToperation performed for transmission of the PUSCH. For example, thechannel access information field set to a first value may indicate afirst type of LBT operation. The channel access information field set toa second value may indicate a second type of LBT operation.

When the first type of LBT operation is used, the terminal may randomlyselect a backoff value within a contention window, and perform a backoffoperation based on the selected backoff value. The backoff value may bedetermined by the contention window, a random variable, and/or anadditional parameter(s). The additional parameter(s) may include apriority of the PUSCH. The size of the contention window may bedetermined according to the priority of the PUSCH. In addition, theadditional parameter(s) may further include configuration information ofa maximum COT (MCOT) and/or the length Td of the defer duration.

When the PUSCH is transmitted based on the UL grant belonging to theRAR, the priority of the PUSCH may have one value. The priority of thePUSCH may be defined in the technical specification. In this case, thebase station may not signal information indicating the priority of thePUSCH to the terminal. The terminal may perform a channel sensingoperation (e.g., energy detection operation) in a time duration (e.g.,defer duration) corresponding to the selected backoff value, andtransmit the MSG3 (e.g., PUSCH including the MSG3) when an energydetection result is less than the energy detection threshold in allsensing slots belonging to the defer duration.

When the second type of LBT operation is used, the terminal may performa channel sensing operation (e.g., energy detection operation) in allsensing slots belonging to the defer duration without a random backoffoperation. When an energy detection result is less than the energydetection threshold in all the sensing slots belonging to the deferduration, the terminal may transmit the MSG3 (e.g., PUSCH including theMSG3). Herein, the length of the defer duration may be several tens ofmicroseconds (e.g., 25 μs or 16 μs).

According to another method, the channel access information field mayindicate three or more values. For example, the channel accessinformation field may indicate at least a first value, a second value, athird value, or a fourth value. The channel access information field setto the first value may indicate the first type of LBT operation. Thechannel access information field set to the second value may indicatethe second type of LBT operation. The channel access information fieldset to the third value may indicate the third type of LBT operation. Thechannel access information field set to the fourth value may indicatethe fourth type of LBT operation.

When the first type of LBT operation is used, the terminal may transmita signal after performing a random backoff operation. The channel accessmethod according to the second type of LBT operation may be the same asthe channel access method according to the third type of LBT operation,and parameter(s) used for the channel access according to the secondtype of LBT operation may be different from parameter(s) used for thechannel access according to the third type of LBT operation. When thesecond type or the third type of the LBT operation is used, the terminalmay perform a channel sensing operation in a preconfigured deferduration without a random backoff operation. However, the length (e.g.,25 μs) of the defer duration according to the second type of LBToperation may be different from the length (e.g., 16 μs) of the deferduration according to the third type of LBT operation. When the fourthtype of LBT operation is used, the terminal may transmit a signalwithout performing the channel sensing operation.

Sequence Field

The UL grant belonging to the RAR may include a sequence field. Thesequence field included in the UL grant may include a scramblingsequence of the PUSCH and/or an initialization sequence of a PUSCHDM-RS. The PUSCH DM-RS may be a DM-RS used for demodulation of thePUSCH. When the above-described sequence is generated based on cellidentification information (e.g., physical cell identifier (PCI)) and/ortime information (e.g., slot index or symbol index), the base stationmay not signal information indicating the sequence (e.g., informationindicated by the sequence field) to the terminal.

HARQ Response Method for an MSG4 in an Unlicensed Band

In the exemplary embodiments shown in FIGS. 4A and 4B, the base stationmay transmit DL-DCI including scheduling information of the MSG4 to theterminal, and transmit the MSG4 through a PDSCH indicated by thescheduling information included in the DL-DCI. The terminal may receivethe DL-DCI from the base station, and may receive the MSG4 from the basestation through the PDSCH indicated by the scheduling informationincluded in the DL-DCI. The terminal may generate an HARQ response forthe MSG4, and may transmit the HARQ response to the base station througha PUCCH or a PUSCH.

In order to transmit the PUCCH including the MSG4, the base station mayinform the terminal of time resource information of the PUCCH, frequencyresource information of the PUCCH, and sequence information. The timeresource information of the PUCCH, frequency resource information of thePUCCH, and sequence information may be included in the DL-DCI (e.g.,DL-DCI including the scheduling information of the MSG4). Some of theconfiguration information (hereinafter, referred to as ‘partialconfiguration information’) of the PUCCH may be indicated by the DL-DCI,and the remaining configuration information of the PUCCH may beindicated to the terminal before the transmission of the PUCCH. Variousmethods may be applied according to a DL transmission.

MSG4 Including Resource Allocation Information of PUCCH

In a proposed method, the base station may transmit the MSG4 includingresource allocation information of the PUCCH to the terminal. Theterminal may receive the MSG4 from the base station, and may identifythe resource allocation information of the PUCCH included in the MSG4.The terminal may determine that a collision has not occurred when theMSG4 is successfully received. Therefore, the resource allocationinformation of the PUCCH may be indicated by the MSG4 or a DLtransmission before the MSG4.

On the other hand, when the MSG4 is not received from the base station,it may be preferable for the terminal to transmit NACK for the MSG4 tothe base station. Since a reason of the NACK for the MSG4 is a channelfading, it may be preferable that the base station retransmits the MSG4to the terminal. When the base station does not retransmit the MSG4 tothe terminal, the terminal may need to perform the initial accessprocedure again because the terminal does not know whether the failureof the MSG4 reception is due to a collision or a channel fading.

In an unlicensed band, the MSG4 may include resource allocationinformation (e.g., slot offset) of a PUCCH and/or information indicatingthe type of LBT operation (e.g., LBT category 2 or LBT category 4). Inaddition, the MSG4 may include information indicating a transmissionscheme (e.g., trigger scheme or non-trigger scheme) of the PUCCH.

When the MSG4 includes the resource allocation information of the PUCCHand the reception of the MSG4 fails, the terminal may not transmit NACKfor the MSG4 to the base station through the PUCCH because the terminaldoes not know the resource allocation information of the PUCCH. In orderto solve this problem, the base station may inform the terminal of theresource allocation information of the PUCCH through the DL-DCIscheduling the MSG4 or a DL transmission before the DL-DCI.

MSG2 and/or Other DL Channel Including Resource Allocation Informationof PUCCH

The base station may transmit a RAR (e.g., MSG2) including partialconfiguration information of the configuration information (e.g.,resource allocation information) of the PUCCH, and may transmit a DLchannel (e.g., the DL-DCI scheduling the MSG4, the MSG4, or acombination of the DL-DCI and the MSG4) including the remainingconfiguration information of the PUCCH. The terminal may identify theconfiguration information (e.g., resource allocation information) of thePUCCH based on the RAR and DL channel received from the base station.When the remaining configuration information of the PUCCH is included inthe DL-DCI, the resource allocation information (i.e., the remainingconfiguration information) of the PUCCH may be explicitly included inthe DL-DCI. Alternatively, the resource allocation information of thePUCCH may be indicated based on a function of an index of a controlchannel element (CCE) to which the DL-DCI is mapped. Alternatively, theresource allocation information of the PUCCH may be indicated based on acombination of a field included in the DL-DCI and the index of the CCEto which the DL-DCI is mapped.

Since the MSG2 is transmitted before the transmission of the MSG4, theMSG2 may include the resource allocation information of the PUCCH (e.g.,the PUCCH on which the HARQ response for the MSG4 is transmitted). Forexample, the MSG2 may include the resource allocation information of thePUCCH on which the HARQ response for the MSG4 is transmitted as well asthe UL grant for the MSG3.

Since the RAR is transmitted to unspecified terminal(s), the resourceallocation information of the PUCCH included in the RAR may be used by aplurality of terminals. That is, the RAR may include common resourceallocation information, and the common resource allocation informationmay indicate the PUCCH on which the HARQ response for the MSG4 istransmitted. Accordingly, the terminals may transmit HARQ responses forthe MSG4 through the same PUCCH. When the collision (e.g., contention)between the terminals is not resolved, the base station may receive ACKfor the MSG4 from the first terminal and NACK for the MSG4 from thesecond terminal through the PUCCH. In this case, the base station maydetermine that there is a collision between the terminals. That is, thebase station may determine that the contention has not been resolved.When only the ACK for the MSG4 is received through the PUCCH, the basestation may determine that the collision between the terminals has beenresolved.

The partial configuration information of the PUCCH included in the RARmay not include time resource information of the PUCCH through which theHARQ response for the MSG4 is transmitted. For example, the RAR mayinclude sequence information of the PUCCH, frequency allocationinformation (e.g., interlace index) of the PUCCH, sequence informationof the PUCCH DM-RS, and the like. The remaining configurationinformation of the PUCCH not included in the RAR may include timeresource information (e.g., slot offset) of the PUCCH and/or informationindicating the LBT type (e.g., LBT category 2 or LBT category 4). Inaddition, the configuration information of the PUCCH may includeinformation indicating a transmission scheme (e.g., trigger scheme ornon-trigger scheme) of the PUCCH.

RAR and DL-DCI

The RAR may include resource set information of the PUCCH. The basestation may transmit the RAR including the resource set information ofthe PUCCH used in the initial access procedure to unspecifiedterminal(s). The resource set information of the PUCCH included in theRAR may include information indicating the first symbol of the PUCCH,the number of symbols constituting the PUCCH in the time domain, and/orthe interlace index(es) of the PUCCH. The remaining configurationinformation of the PUCCH not included in the RAR may be transmittedthrough a DL channel.

The terminal may receive a SS/PBCH block from the base station, and mayobtain cell identification information from the SS/PBCH block. Theterminal may initialize the sequence of the PUCCH DM-RS using the cellidentification information. The terminal may perform a scramblingoperation on data and/or control information transmitted through anuplink channel (e.g., PUCCH) using the cell identification information.

The DL-DCI scheduling the MSG4 may include a PUCCH resource indicator, aslot offset for transmitting an HARQ response, and/or informationindicating a transmission scheme of the PUCCH (e.g., trigger A field).When the remaining configuration information of the PUCCH is included inthe DL-DCI, the resource allocation information (i.e., the remainingconfiguration information) of the PUCCH may be explicitly included inthe DL-DCI scheduling the MSG4. Alternatively, the resource allocationinformation of the PUCCH may be indicated based on a function of anindex of a CCE to which the DL-DCI is mapped. Alternatively, theresource allocation information of the PUCCH may be indicated based on acombination of the field included in the DL-DCI and the index of the CCEto which the DL-DCI is mapped. In addition, the DL-DCI scheduling theMSG4 may further include an offset of the first symbol in which thePUCCH is transmitted. The offset may indicate that the transmission timepoint of the PUCCH is the start time point of the symbol (e.g., symbolboundary), after 16 μs or 25 μs from the start time point of the symbol,or after ((16 μs or 25 μs)+TA) from the start time point of the symbol.

The configuration information of the PUCCH may be included in the RMSIas well as the RAR. The reason is that when the size of the HARQresponse for the MSG4 is 1 bit, the number of bits required forindicating the resource of the PUCCH is small. When the initial accessprocedure is performed in a licensed band, the configuration informationof the PUCCH through which the HARQ response for the MSG4 is transmittedmay be included in the RMSI. In the RRC connection reconfigurationprocedure, the configuration information of the PUCCH may not beindicated by the RAR. In this case, the base station may inform theterminal of the configuration information of the PUCCH through separatesignaling.

RMSI and DL Channel Including Resource Allocation Information of PUCCH

The base station may transmit the RMSI including the partialconfiguration information of the configuration information (e.g.,resource allocation information) of the PUCCH, and the DL channelincluding the remaining configuration information of the PUCCH (e.g.,DL-DCI scheduling the MSG4, the MSG4, the RAR, or a combination of twoor more among the DL-DCI, the MSG4, and the RAR). The terminal mayidentify the configuration information (e.g., resource allocationinformation) of the PUCCH based on the RAR and the DL channel receivedfrom the base station. When the remaining configuration information ofthe PUCCH is included in the DL-DCI, the resource allocation information(i.e., the remaining configuration information) of the PUCCH may beexplicitly included in the DL-DCI. Alternatively, the resourceallocation information of the PUCCH may be indicated based on a functionof an index of the CCE to which the DL-DCI is mapped. Alternatively, theresource allocation information of the PUCCH may be indicated based on acombination of the field included in the DL-DCI and the index of the CCEto which the DL-DCI is mapped.

In the NR communication system operating in a licensed band, the basestation may transmit an RMSI including resource sets of the PUCCH to anunspecified terminal(s), and may transmit to the terminal DL-DCI (e.g.,DL-DCI scheduling the MSG4) indicating one element among the resourcesets of the PUCCH included in the RMSI. The terminal may receive theRMSI from the base station, and may identify the resource sets of thePUCCH included in the RMSI. In addition, the terminal may receive theDL-DCI scheduling the MSG4 from the base station, select one resourcefrom the resource sets of the PUCCH based on the information included inthe DL-DCI, and use the selected resource to transmit the HARQ responsefor the MSG4 to the base station.

Since the RMSI is transmitted to unspecified terminal(s), the resourceallocation information of the PUCCH included in the RMSI may be used bya plurality of terminals. That is, the RMSI may include common resourceallocation information, and the common resource allocation informationmay indicate a PUCCH through which the HARQ response for the MSG4 istransmitted. Accordingly, the terminals may transmit HARQ responses forthe MSG4 through the same PUCCH. When the collision (e.g., contention)between the terminals is not resolved, the base station may receive ACKfor the MSG4 from the first terminal and NACK for the MSG4 from thesecond terminal through the PUCCH. In this case, the base station maydetermine that there is a collision between the terminals. That is, thebase station may determine that the contention has not been resolved.When only the ACK for the MSG4 is received through the PUCCH, the basestation may determine that the collision between the terminals has beenresolved.

The partial configuration information of the PUCCH included in the RMSImay not include time resource information of the PUCCH through which theHARQ response for the MSG4 is transmitted. For example, the RMSI mayinclude sequence information of the PUCCH, frequency allocationinformation (e.g., interlace index) of the PUCCH, sequence informationof the PUCCH DM-RS, and the like. The remaining configurationinformation of the PUCCH not included in the RMSI may include timeresource information (e.g., slot offset) of the PUCCH and/or informationindicating the LBT type (e.g., LBT category 2 or LBT category 4). Inaddition, the configuration information of the PUCCH may includeinformation indicating a transmission scheme (e.g., trigger scheme ornon-trigger scheme) of the PUCCH.

RMSI and DL-DCI

The RMSI may include resource set information of the PUCCH. The basestation may transmit the RMSI including the resource set information ofthe PUCCH used in the initial access procedure to unspecifiedterminal(s). The resource set information of the PUCCH included in theRMSI may include information indicating the first symbol of the PUCCH,the number of symbols constituting the PUCCH in the time domain, and/orthe interlace index(es) of the PUCCH. The remaining configurationinformation of the PUCCH not included in the RMSI may be transmittedthrough a DL channel.

The terminal may receive a SS/PBCH block from the base station, and mayobtain cell identification information from the SS/PBCH block. Theterminal may initialize the sequence of the PUCCH DM-RS using the cellidentification information. The terminal may perform a scramblingoperation on data and/or control information transmitted through anuplink channel (e.g., PUCCH) using the cell identification information.

The DL-DCI scheduling the MSG4 may include a PUCCH resource indicator, aslot offset for transmitting an HARQ response, and/or informationindicating a transmission scheme of the PUCCH (e.g., trigger A field).Also, the DL-DCI scheduling the MSG4 may further include an offset ofthe first symbol in which the PUCCH is transmitted. The offset mayindicate that the transmission time point of the PUCCH is the start timepoint of the symbol (e.g., symbol boundary), after 16 μs or 25 μs fromthe start time point of the symbol, or after ((16 μs or 25 μs)+TA) fromthe start time point of the symbol.

When the remaining configuration information of the PUCCH is included inthe DL-DCI, the resource allocation information (i.e., the remainingconfiguration information) of the PUCCH may be explicitly included inthe DL-DCI scheduling the MSG4. Alternatively, the resource allocationinformation of the PUCCH may be indicated based on a function of anindex of the CCE to which the DL-DCI is mapped. Alternatively, theresource allocation information of the PUCCH may be indicated based on acombination of the field included in the DL-DCI and the index of the CCEto which the DL-DCI is mapped.

The resource allocation information of the PUCCH included in the RMSImay be used in the RRC connection reconfiguration procedure as well asthe initial access procedure. The base station may transmit an RRCmessage to the terminal through a PDSCH, the terminal may transmit tothe base station an RRC message including an HARQ response (e.g., ACK)for the RRC message received from the base station through a PUSCH.

The resource of the PUCCH in the RRC connection reconfigurationprocedure may be a fallback resource or a default resource. The basestation may transmit the RMSI including information on the fallbackresource of the PUCCH to the terminal. The terminal may receive the RMSIfrom the base station, and may identify the information on the fallbackresource of the PUCCH included in the RMSI. Since the base station doesnot use two or more codewords in the initial access procedure or the RRCconnection reconfiguration procedure, the size of the HARQ response maybe 1 bit.

MSG4 Including UL Gran in a Communication System Operating in anUnlicensed Band

In the initial access procedure, the base station may transmit the MSG4through the PDSCH and may receive the HARQ response for the MSG4 fromthe terminal. When ACK for the MSG4 is received, the base station maydetermine that the collision between the terminals has been resolved,and may determine that the RRC connection with the correspondingterminal is established. Thereafter, the base station may perform aprocedure for exchanging an RRC message with the terminal. Thisoperation may be the exemplary embodiments shown in FIGS. 4A and 4B.

The terminal transmitting the ACK for the MSG4 may establish an RRCconnection with the base station. Thereafter, the terminal may exchangeother RRC messages (e.g., MSG5, UE capability signaling message, etc.)with the base station. Prior to the transmission/reception procedure ofthe MSG5, the base station may transmit control information to theterminal using PHY signaling and/or MAC signaling.

The MSG5 may be an RRC message transmitted from the terminal aftertransmission of the MSG4. The MSG5 may be transmitted on the PUSCH. Theterminal may receive the UL grant from the base station, and maytransmit the MSG5 to the base station through the PUSCH indicated by theUL grant. The MSG5 may be an RRC message transmitted and received whenthe RRC connection between the base station and the terminal isestablished. Accordingly, the base station may consider that the MSG5 isreceived from the terminal which transmitted the ACK for the MSG4.

In a proposed method, the PDSCH through which MSG4 is transmitted mayinclude the UL grant for the MSG5. The UL grant for the MSG5 may includeat least one of information indicating a trigger scheme of the PUSCH(e.g., trigger field), a slot offset field for the PUSCH, a start symboland length field for the PUSCH, a start time point field for the PUSCH,a frequency resource field for the PUSCH, a channel access field for thePUSCH, and a sequence field for the PUSCH DM-RS.

The PUSCH including the MSG5 may be transmitted based on the triggerscheme. Therefore, the base station may transmit two UL grants for theMSG5. The PDSCH through which the MSG4 is transmitted may includeinformation for reception of the two UL grants (e.g., a first UL grant,a second UL grant (e.g., common DCI)). The UL grant for the MSG5 mayinclude resource allocation information of the PUSCH, information forreceiving the common DCI (e.g., common identifier information (e.g.,RNTI)), and the like.

The UL grant for scheduling the MSG5 transmission may have various formsand may be transmitted through the PDSCH through which MSG4 istransmitted. For example, the UL grant for the MSG5 may be included inthe MSG4. An encoding operation for the MSG4 including the UL grant maybe performed, and the encoded MSG4 may be mapped to the PDSCH.Alternatively, the UL grant for the MSG5 may be defined as an RRCmessage. In this case, the RRC message composed of the UL grant for theMSG5 may be multiplexed with the RRC message composed of the MSG4. Anencoding operation may be performed on the multiplexed RRC messages, andthe encoded RRC messages may be mapped to a PDSCH. Alternatively, the ULgrant for the MSG5 may be defined as a MAC message (e.g., MAC CE). Inthis case, the MAC message composed of the UL grant for the MSG5 may bemultiplexed with the RRC message composed of the MSG4. An encodingoperation may be performed on the multiplexed messages, and the encodedmessages may be mapped to a PDSCH.

The terminal may receive the UL grant for the MSG5 from the basestation. The terminal may transmit the MSG5, which is an HARQ responseto the MSG4, to the base station based on the UL grant. In this case,the end time point of the initial access procedure may be earlier thanthe end time point of the existing initial access procedure. After theinitial access procedure ends, the exchange procedure of the RRCmessages between the terminal and the base station may be performed.

When the above-described initial access procedure is performed in thecommunication system operating in an unlicensed band, interference onother terminals and/or a channel occupancy time may be minimized. Thus,the throughput of the communication system can be increased. When theproposed methods are used, in consideration of signaling overhead of theresource allocation information of the PUCCH, a time required for thePUCCH transmission, a time required for the UL grant transmission, etc.,there is an advantage that the HARQ response for the MSG4 is not fedback to the base station.

A case when a NACK occurs for the MSG4 in the initial access proceduremay be a case when the MSG4 retransmission procedure fails or a casewhen the collision between terminals has not been resolved. In thiscase, the initial access procedure may be restarted. That is, theterminal may transmit a RA preamble again. When the NACK for the MSG4 isreceived from the terminal in the existing initial access procedure, thebase station may not identify a reason of the NACK for the MSG4 (e.g.,channel fading or collision between terminals).

In a proposed method, when the PUSCH including the MSG5 is received fromthe terminal, the base station may not distinguish between the channelfading and the collision between terminals. In this case, the basestation may reassign the MSG4 to the terminal(s). Since the collision(e.g., contention) between terminals should be resolved within apreconfigured time (e.g., timer for contention resolution,mac-ContentionResolutionTimer), the base station may retransmit the MSG4before the end of the preconfigured time.

Method of Triggering MSG5

In the following exemplary embodiments, the slot in which the MSG4 isreceived may be referred to as a slot n. When the trigger fieldbelonging to the UL grant indicates a first value (e.g., ‘0’), theterminal may transmit a PUSCH to the base station in a slot n+l+k basedon one UL grant (e.g., first UL grant). Here, l may be indicated fromthe base station to the terminal through higher layer signaling. Forexample, l may be 3 or 4. When l is not indicated by higher layersignaling, l may be one (e.g., 4) of a plurality of values (e.g.,natural numbers).

Here, k may mean an offset included in the UL grant. The base stationmay inform k to the terminal. Alternatively, k may be one of valuesdefined in the technical specification. For example, referring to Table8-2d of 3GPP TS 36.213, k may have a value from 0 to 15. The UL grantmay include an index indicating k, and the size of the index indicatingk may be 4 bits. The terminal may determine a slot for transmitting thePUSCH by performing the LBT operation. For example, the terminal maytransmit the PUSCH in a slot n+l+k+i. Here, i=0, 1, . . ., N-1′ may bedefined, and N may indicate the number of PUSCHs. N may be a naturalnumber. N may be fixed to one value according to the type of the ULgrant (e.g., the format of the UL grant, the format of the UL-DCI,RNTI).

On the other hand, when the trigger field belonging to the UL grant(e.g., first UL grant) indicates a second value (e.g., ‘1’), theterminal may receive an additional UL grant (e.g., second UL grant orcommon DCI), and may transmit a PUSCH based on the additional UL grant.Here, it may be assumed that the terminal receives the common DCI in aslot m. The slot n may be identical to the slot m. Alternatively, theslot n may be different from the slot m. When the slot n is differentfrom the slot m, the slot m may be located after the slot n. When a timeinterval between the slot n and the slot m is greater than or equal to atime interval defined in the technical specification, the UL grant(e.g., UL grant received in the slot n and/or the slot m) may beconsidered invalid.

For example, in Table 8-2f of TS 36.213, four maximum time intervals ofa slot or subframe are defined. The index included in the UL grant mayindicate one of the four maximum time intervals defined in the technicalspecification. The terminal may identify the maximum time interval basedon the index included in the UL grant received from the base station,and may determine that the corresponding UL grant is invalid when thetime interval between the slot n and the slot m is greater than or equalto the maximum time interval.

In addition, the common DCI may include a trigger field. The identifier(e.g., RNTI) used for scrambling of the common DCI (e.g., cyclicredundancy check (CRC) of the common DCI) may be different from theidentifier used for scrambling of the UL grant. When the trigger fieldof the common DCI indicates a first value (e.g., ‘1’), the terminal maytransmit a PUSCH in a slot m+l+k. Here, k may be an offset included inthe UL grant. The base station may inform k to the terminal using higherlayer signaling. Alternatively, k may be defined in the technicalspecification. For example, k defined in Table 8-2e of 3GPP TS 36.213may be set to a value from 0 to 3. The UL grant may include an indexindicating k, and the size of the index indicating k may be 2 bits.

The UL offset 1 and a UL duration d may be derived from a specific indexincluded in the common DCI. The base station may inform the terminal ofone of specific indexes defined in the technical specification. Forexample, 32 specific indexes are defined in Table 13A-2 of 3GPP TS36.213. The base station may transmit DCI including informationindicating one specific index among the 32 specific indexes to theterminal.

The terminal may determine a slot for transmitting the PUSCH byperforming the LBT operation. For example, the terminal may transmit thePUSCH in a slot n+l+k+i. Here, ‘i=0, 1, . . . , N-1’ may be defined, andN may indicate the number of PUSCHs. N may be a natural number. N may befixed to one value according to the type of the UL grant (e.g., theformat of the UL grant, the format of the UL-DCI, RNTI). The terminalmay not receive the PDCCH in slot(s) in which the PUSCH can betransmitted, and the corresponding slot(s) may be a slot m+l+i. i may bedefined as ‘i=0, 1, . . . , d-1’.

MSG5 to Which a Common DCI is Applied

The UL grant belonging to the MSG4 may include information indicatingthe type of LBT operation performed for transmission of the MSG5.Accordingly, the terminal may identify the type of LBT operationperformed for transmission of the MSG5 based on the information includedin the UL grant belonging to the MSG4. The type of LBT operationindicated by the UL grant belonging to the MSG4 may be the LBT category2 (hereinafter referred to as ‘C2 LBT’) or LBT category 4 (hereinafterreferred to as ‘C4 LBT’).

When the UL grant belonging to the MSG4 indicates the C4 LBT, theterminal may identify whether a PUSCH can be transmitted in a radioresource indicated by the UL grant by performing the C4 LBT operation.In a time duration (e.g., COT) secured by the base station performingthe LBT operation, even when the UL grant belonging to the MSG4indicates the C4 LBT, the terminal may perform the C2 LBT operation foruplink transmission. Accordingly, the terminal may determine whether atime resource (e.g., slot or subframe) for transmitting the PUSCHbelongs to the time duration (e.g., COT) secured by the base station.

In order to support this operation, the base station may transmit DCIincluding configuration information of the COT secured by the LBToperation to terminal(s). The configuration information of the COT mayinclude information on a pattern of slot(s) or subframe(s) belonging tothe COT. The pattern information may include one or more of the numberof DL slots, the number of UL slots, the number of slots composed of DLsymbols, UL symbols, and FL symbols, an order of slots, and an order ofsymbols. The pattern information may be represented as a bitmap or anindex. The DCI (e.g., common DCI) including the configurationinformation of the COT may be transmitted to unspecified terminal(s).Therefore, the DCI including the configuration information of the COT(e.g., CRC of the DCI) may be scrambled based on the common RNTI.

The common DCI may include time window information (e.g., the number ofslots or the number of subframes constituting a time window). The timewindow information included in the common DCI may indicate timeresource(s) to which the C2 LBT operation is applicable. The terminal(s)may perform the C2 LBT operation for transmission of the PUSCH in thetime resource(s) indicated by the time window information included inthe common DCI.

Method of Applying an Orthogonal Cover Code (OCC) to a Sequence-BasedPUCCH

The UCI may be composed of one or two bits. In this case, a PUCCHincluding the UCI may be defined based on a scheme of applying aspreading sequence. By appending preconfigured bit(s) to the existingUCI, it is possible to generate a UCI consisting of three bits. Forexample, a UCI composed of 3 bits may be generated by adding (3-a) 0'sto a UCI composed of a bits in a channel encoding procedure. Forexample, when the Reed Muller code is applied, a codeword may beexpressed as a linear combination of a result (e.g., a column vector ora row vector of a matrix) of a product between a matrix defined in thetechnical specification and the UCI. In particular, when the UCIconsists of one bit, it may be interpreted that the UCI is spread to avector defined by the Reed Muller code.

When the PUCCH is transmitted in an unlicensed band, in order to satisfythe frequency regulation, PRBs belonging to the resource of the PUCCHmay be arranged to have a predetermined interval in the entire frequencyband. For example, the PRBs belonging to the PUCCH resource may have aninterlace structure. This operation may mean that the number ofterminals FDMed in the entire frequency band is the same as the numberof interlaces. When a small number of bits of information aretransmitted by one terminal through the PUCCH, many terminals may bemultiplexed in the entire frequency band. In particular, there is a needfor a method in which PUCCHs (e.g., UCIs of different terminals) usingthe same interlace can be multiplexed. It may be preferable to apply aspreading code to a part of the PUCCH through which the UCI composed of1 bit or more is transmitted.

In a proposed method, an OCC may be applied symbol by symbol in the timedomain. In this case, the number z of symbols of the PUCCH may be thelength of the OCC. To support this operation, the DM-RS may bepreferably mapped to the same resource elements (REs) in the PRB. Forexample, the OCC may be a discrete Fourier transform (DFT) sequence or aHadamard sequence. When z is expressed as an exponential power of 2, itmay be preferable to apply the Hadamard sequence. Otherwise, it may bepreferable to apply the DFT sequence.

Method of Multiplexing DM-RS and UCI in the Frequency Domain

The number of symbols constituting the PUCCH resource may be smallerthan a preconfigured number (e.g., four). For example, the number ofsymbols constituting the PUCCH resource may be one or two. In this case,the PUCCH DM-RS may be multiplexed with the UCI (e.g., REs to which theencoded UCI is mapped) in the frequency domain. Here, the PUCCH DM-RSmay be a DM-RS used for demodulation of the PUCCH (e.g., UCI). In onesymbol belonging to the PUCCH resource, the number of REs to which theDM-RS is mapped (hereinafter referred to as ‘DM-RS REs’) among REsincluded in one PRB may be x, and the number of REs to which the UCI ismapped (Hereinafter, referred to as ‘UCI REs’) may be y (=12-x). Each ofx and y may be a natural number. The UCI REs may be REs to which theencoded UCI is mapped.

In a proposed method, the OCC having the length of y may be applied tothe UCI REs. As the OCC having the length of y is applied to the UCIREs, the number of PUCCHs multiplexed in the frequency domain mayincrease. That is, a multiplexing capability or multiplexing order mayincrease.

On the other hand, the OCC may be applied on a PRB basis. Since theinterlace for the PUCCH includes discontinuous PRBs, it may bepreferable for the OCC to be applied to one PRB. The reason is that whena spreading code is applied such that discontinuous PRBs arecode-division-multiplexed with each other, due to frequency selectivecharacteristics of a radio channel, frequency resources to which thespreading code is mapped may have different channel values. Therefore,the decoding performance of the spreading code may be degraded. The OCCmay be a DFT sequence or a Hadamard sequence. When y is represented asan exponential power of 2, the Hadamard sequence may be applied.

Method of Multiplexing DM-RS and UCI in the Time Domain

When the number of symbols constituting the PUCCH resource is more thana preconfigured number (e.g., four), the PUCCH DM-RS may be multiplexedwith the UCI (e.g., REs to which the encoded UCI is mapped) in the timedomain. In this case, the OCC may be applied in the same manner as theabove-described exemplary embodiments. The OCC may be applied within onePRB among PRBs constituting the PUCCH. The number of UCI REs included inone PRB may be twelve.

In a proposed method, the OCC having the length of 12 may be applied tothe UCI REs. Therefore, the number of PUCCHs multiplexed in the timedomain may increase. The OCC may be a DFT sequence or a Hadamardsequence. For example, a DFT sequence having the length of 12 may beapplied.

Enhanced PUCCH Format 2

When the PUCCH format 2 is used in the NR communication system, fourDM-RS REs and eight UCI REs may be allocated in one PRB. Thus, an OCChaving a length of 8 may be applied to the UCI REs. For example, the OCCmay be a Hadamard sequence or a DFT sequence.

In order to apply the OCC step by step, a recursively defined Hadamardsequence may be applied. A Hadamard sequence having a length of 2^(n+1)may be obtained by repeatedly adding a Hadamard sequence having a lengthof 2 to a Hadamard sequence having a length of 2^(n).

The Hadamard sequences may have indexes having various orders. These maybe represented by a matrix. The index of the Hadamard sequence may beassigned according to the order of the column vectors of the matrix.Tables 2 to 4 below may show Hadamard sequences having different orders.In Tables 2 to 4, a horizontal axis may represent an RE index in a PRB,and in Tables 2 to 5, a vertical axis may represent an index of asequence (e.g., Hadamard sequence). In Tables 2 to 4, ‘+1’ and ‘−1’ maymean a value of the Hadamard sequence.

Table 1 below may represent a matrix of Reed Muller codes. When the UCIis 1 bit in size, a codeword may be obtained by multiplying the ReedMuller code (e.g., generation matrix defined in Table 1) and a rowvector (e.g., 11 information bits generated by appending zero(s) toinformation or information bits). According to this operation, a vectorconsisting of 32 1's (i.e., [1, 1, . . . , 1]) may be represented. TheUCI may be spread by the Hadamard sequence, and the spread UCI may bemapped to all PRBs of the interlace for the PUCCH.

TABLE 1 0 1 2 3 4 5 6 7 8 9 10  0 1 1 0 0 0 0 0 0 0 0 1  1 1 1 1 0 0 0 00 0 1 1  2 1 0 0 1 0 0 1 0 1 1 1  3 1 0 1 1 0 0 0 0 1 0 1  4 1 1 1 1 0 00 1 0 0 1  5 1 1 0 0 1 0 1 1 1 0 1  6 1 0 1 0 1 0 1 0 1 1 1  7 1 0 0 1 10 0 1 1 0 1  8 1 1 0 1 1 0 0 1 0 1 1  9 1 0 1 1 1 0 1 0 0 1 1 10 1 0 1 00 1 1 1 0 1 1 11 1 1 1 0 0 1 1 0 1 0 1 12 1 0 0 1 0 1 0 1 1 1 1 13 1 1 01 0 1 0 1 0 1 1 14 1 0 0 0 1 1 0 1 0 0 1 15 1 1 0 0 1 1 1 1 0 1 1 16 1 11 0 1 1 1 0 0 1 0 17 1 0 0 1 1 1 0 0 1 0 0 18 1 1 0 1 1 1 1 1 0 0 0 19 10 0 0 0 1 1 0 0 0 0 20 1 0 1 0 0 0 1 0 0 0 1 21 1 1 0 1 0 0 0 0 0 1 1 221 0 0 0 1 0 0 1 1 0 1 23 1 1 1 0 1 0 0 0 1 1 1 24 1 1 1 1 1 0 1 1 1 1 025 1 1 0 0 0 1 1 1 0 0 1 26 1 0 1 1 0 1 0 0 1 1 0 27 1 1 1 1 0 1 0 1 1 10 28 1 0 1 0 1 1 1 0 1 0 0 29 1 0 1 1 1 1 1 1 1 0 0 30 1 1 1 1 1 1 1 1 11 1 31 1 0 0 0 0 0 0 0 0 0 0

TABLE 2 0 2 3 5 6 8 9 11 0 +1 +1 +1 +1 +1 +1 +1 +1 1 +1 +1 +1 +1 −1 −1−1 −1 2 +1 +1 −1 −1 −1 −1 +1 +1 3 +1 +1 −1 −1 +1 +1 −1 −1 4 +1 −1 −1 +1+1 −1 −1 +1 5 +1 −1 −1 +1 −1 +1 +1 −1 6 +1 −1 +1 −1 −1 +1 −1 +1 7 +1 −1+1 −1 +1 −1 +1 −1

TABLE 3 0 2 3 5 6 8 9 11 0 +1 +1 +1 +1 +1 +1 +1 +1 1 +1 +1 +1 +1 −1 −1−1 −1 2 +1 +1 −1 −1 +1 +1 −1 −1 3 +1 +1 −1 −1 −1 −1 +1 +1 4 +1 −1 +1 −1+1 −1 +1 −1 5 +1 −1 +1 −1 −1 +1 −1 +1 6 +1 −1 −1 +1 +1 −1 −1 +1 7 +1 −1−1 +1 −1 +1 +1 −1

TABLE 4 0 2 3 5 6 8 9 11 0 +1 +1 +1 +1 +1 +1 +1 +1 1 +1 −1 +1 −1 +1 −1+1 −1 2 +1 +1 −1 −1 +1 +1 −1 −1 3 +1 −1 −1 +1 +1 −1 −1 +1 4 +1 +1 +1 +1−1 −1 −1 −1 5 +1 −1 +1 −1 −1 +1 −1 +1 6 +1 +1 −1 −1 −1 −1 +1 +1 7 +1 −1−1 +1 −1 +1 +1 −1

One or more OCC indexes among eight OCC indexes (e.g., indexes of theHadamard sequences) may be used. The number of the one or more OCCindexes may be w, and w may be less than eight. In this case, w OCCindexes (e.g., 0, 1, . . ., w-1) defined in Table 4 may be used inorder. This is because the OCC may be interpreted as an OCC subsequencebased on adjacent REs (e.g., REs to which the OCC is to be applied).Since the DM-RS is mapped to REs 1, 4, 7, and 10 in a PRB, two UCI REslocated between adjacent DM-RS REs may form a subsequence of the OCC. Itmay be preferable for subsequences of the OCC to form one OCC. Becauseof the nested characteristics of the OCC being established in stages,the above-described exemplary embodiments may be preferably used in aradio channel having a frequency selective characteristic.

Enhanced PUCCH Format 3

When the PUCCH format 3 is used in the NR communication system, 12 UCIREs may be allocated. Thus, an OCC having a length of 12 may be appliedto the UCI REs. For example, the OCC may be a DFT sequence. The DFTsequence may be a column vector of a DFT matrix. Table 5 below mayrepresent DFT sequences. A horizontal axis of Table 5 may represent anRE index in the PRB, and the vertical axis of Table 5 may represent anOCC index. In Table 5, w may be e^(2π1/12).

TABLE 5 0 1 2 3 4 5 6 7 8 9 10 11  0 ω⁰ ω⁰ ω⁰ ω⁰ ω⁰ ω⁰ ω⁰ ω⁰ ω⁰ ω⁰ ω⁰ ω⁰ 1 ω⁰ ω¹ ω² ω³ ω⁴ ω⁵ ω⁶ ω⁷ ω⁸ ω⁹ ω¹⁰ ω¹¹  2 ω⁰ ω² ω⁴ ω⁶ ω⁸ ω¹⁰ ω¹² ω¹⁴ω¹⁶ ω¹⁸ ω²⁰ ω²²  3 ω⁰ ω³ ω⁶ ω⁹ ω¹² ω¹⁵ ω¹⁸ ω²¹ ω²⁴ ω²⁷ ω³⁰ ω³³  4 ω⁰ ω⁴ω⁸ ω¹² ω¹⁶ ω²⁰ ω²⁴ ω²⁸ ω³² ω³⁶ ω⁴⁰ ω⁴⁴  5 ω⁰ ω⁵ ω¹⁰ ω¹⁵ ω²⁰ ω²⁵ ω³⁰ ω³⁵ω⁴⁰ ω⁴⁵ ω⁵⁰ ω⁵⁵  6 ω⁰ ω⁶ ω¹² ω¹⁸ ω²⁴ ω³⁰ ω³⁶ ω⁴² ω⁴⁸ ω⁵⁴ ω⁶⁰ ω⁶⁶  7 ω⁰ω⁷ ω¹⁴ ω²¹ ω²⁸ ω³⁵ ω⁴² ω⁴⁹ ω⁵⁶ ω⁶³ ω⁷⁰ ω⁷⁷  8 ω⁰ ω⁸ ω¹⁶ ω²⁴ ω³² ω⁴⁰ ω⁴⁸ω⁵⁶ ω⁶⁴ ω⁷² ω⁸⁰ ω⁸⁸  9 ω⁰ ω⁹ ω¹⁸ ω²⁷ ω³⁶ ω⁴⁵ ω⁵⁴ ω⁶³ ω⁷² ω⁸¹ ω⁹⁰ ω⁹⁹ 10ω⁰ ω¹⁰ ω²⁰ ω³⁰ ω⁴⁰ ω⁵⁰ ω⁶⁰ ω⁷⁰ ω⁸⁰ ω⁹⁰ ω¹⁰⁰ ω¹¹⁰ 11 ω⁰ ω¹¹ ω²² ω³³ ω⁴⁴ω⁵⁵ ω⁶⁶ ω⁷⁷ ω⁸⁸ ω⁹⁹ ω¹¹⁰ ω¹²¹

One or more OCC indexes among 12 OCC indexes may be used. The number ofthe one or more OCC indexes may be q, and q may be less than 12. Inorder to select q OCC indexes, a satisfying (ω^(α))^(q)=1 may beselected. α may be preferably selected from Table 5. The reason is thatthe selected column vectors have a property of being orthogonal to eachother. In addition, since arguments of complex values of the q-th rootsof unity have a constant interval, the above-described exemplaryembodiments may be preferably applied to a radio channel having afrequency selective characteristic.

HARQ Response Feedback Method in a Shared Spectrum

The PUCCH resource may include a PUCCH format, a frequency resource ofthe PUCCH, a time resource of the PUCCH, and a sequence resource for thePUCCH. When the size of the UCI is 3 bits or more, a Reed Muller code ora Polar code may be used in the encoding procedure of the UCI, and theencoded UCI may be mapped to the PUCCH. When the size of the UCI is 1bit or 2 bits, a UCI having a size of 3 bits or more may be generated byappending a predefined bit(s) (e.g., ‘0’) to the UCI in the encodingprocedure of the UCI.

The PUCCH DM-RS may be TDMed or FDMed with a codeword of the UCI. Forexample, when the number of symbols constituting the PUCCH is small, thePUCCH DM-RS may be FDMed with the codeword of the UCI. Here, the numberof symbols constituting the PUCCH may be one or two. When the number ofsymbols constituting the PUCCH is large, the PUCCH DM-RS may be TDMedwith the codeword of the UCI. Here, the number of symbols constitutingthe PUCCH may be three or more.

The base station may transmit an RRC message including a resource set ora resource list of the PUCCH to the terminal. In addition, the basestation may transmit DL-DCI including information (e.g., an index)indicating one or more resources belonging to the resource set or theresource list indicated by the RRC message to the terminal. Here, theDL-DCI may include resource allocation information of a PDSCH. Theterminal may receive the RRC message from the base station, and mayidentify the resource set or the resource list of the PUCCH included inthe RRC message. In addition, the terminal may receive the DL-DCIscheduling the PDSCH from the base station, and may identify the one ormore resources indicated by the DL-DCI among the resources belonging tothe resource set or the resource list of the PUCCH, and transmit a PUCCHto the base station by using the identified one or more resources.

The PUCCH resource may be fixed to one, and additional information maybe needed to transmit the PUCCH. For example, when an HARQ response forthe PDSCH is transmitted through the PUCCH, a slot corresponding to anHARQ-ACK feedback timing may be indicated by a slot offset. In addition,transmission of the PUCCH in a shared spectrum may be performed based onthe trigger scheme.

In a proposed method, the DL-DCI scheduling the PDSCH may include otherinformation (e.g., time resource information (e.g., slot offset) andtrigger scheme for the PUCCH transmission). The size of the DL-DCI maybe increased to include the other information. Since one DCI includesresource allocation information of one PDSCH and feedback information(e.g., configuration information of PUCCH) of the HARQ response for thePDSCH, the burden of the decoding procedure of the PDCCH may notincrease.

In another proposed method, the other information (e.g., time resourceinformation (e.g., slot offset) and trigger scheme for the PUCCHtransmissions) may be included in another DCI (e.g., a common DCI or aUL-DCI scheduling the PUSCH) instead of the DL-DCI scheduling the PDSCH.The terminal may receive the UL-DCI including the other information. Inthis case, the terminal may transmit the HARQ response by using thePUSCH instead of the PUCCH. The DL-DCI may include resource allocationinformation of the PUCCH and may not include information indicating atrigger scheme of the PUCCH transmission and/or information indicating achannel access scheme of the PUCCH. Accordingly, the size of the DL-DCImay be reduced. In this case, the terminal receives two DCIs (e.g.,DL-DCI scheduling the PDSCH, and UL-DCI including information fortransmitting the HARQ response) to perform a reception operation of thePDSCH and an HARQ response transmission operation for the PDSCH.Therefore, the burden of the decoding procedure of the PDCCH mayincrease.

Method of Indicating PUCCH Transmission Using DL-DCI

The DL-DCI may include one or more of the following fields, and theDL-DCI including one or more fields may indicate PUCCH transmission.

Trigger Field for PUCCH

The DL-DCI may include a trigger field. The number of trigger fields mayvary depending on the trigger scheme of the PUCCH. One trigger field(e.g., trigger A field) or two trigger fields (e.g., trigger A field andtrigger B field) may be needed for triggering the PUCCH transmission.The trigger A field and the trigger B field may be included in differentDL-DCIs.

The trigger A field included in the DL-DCI may indicate two differentvalues. The terminal may determine whether to perform a monitoringoperation of the trigger B field according to a value indicated by thetrigger A field. The trigger A field set to a first value (e.g., ‘0’)may indicate the non-trigger scheme. In this case, the terminal maytransmit the PUCCH based on the DL-DCI. For example, the terminal mayidentify a slot in which the PUCCH can be transmitted based on the slotoffset field included in the DL-DCI. The trigger A field set to a secondvalue (e.g., ‘1’) may indicate the trigger scheme. In this case, theterminal may receive an additional DCI (e.g., common DCI) that triggersthe transmission of the PUCCH. The additional DCI may include thetrigger B field. The terminal may identify a slot in which the PUCCH canbe transmitted based on information element(s) (e.g., trigger B field)included in the additional DCI.

Slot Offset Field for PUCCH

The DL-DCI may include a slot offset field. The slot in which the HARQresponse is transmitted may be indicated by the slot offset fieldincluded in the DL-DCI. For example, the terminal may determine a slotafter an offset indicated by the slot offset field from the slot inwhich the PDSCH is received as a slot in which the PUCCH (e.g., PUCCHincluding the HARQ response) is transmitted. The terminal may performthe LBT operation and may not transmit the PUCCH in the slot indicatedby the slot offset field when the channel is determined to be busy as aresult of the LBT operation.

The slot offset field for the PUCCH may indicate an integer or anon-numerical value. When the slot offset field indicates an integer,the terminal may determine a slot after the value indicated by the slotoffset field from the slot in which the PDSCH is received as the slot inwhich the PUCCH is transmitted. On the other hand, when the slot offsetfield indicates a non-numeric value, the terminal may not transmit thePUCCH when an additional indication (e.g., an additional DCI triggeringone or more transmissions among HARQ codebook(s)) is not received fromthe base station.

HARQ-ACK Codebook Group Indicator

HARQ response bits indicated to be transmitted in the same PUCCH may beassumed to belong to the same HARQ codebook. The PUCCH transmitted inthe unlicensed band may include one HARQ codebook. The HARQ codebook maybe a bit string composed of HARQ response bits, and one HARQ codebookmay correspond to one PUCCH transmission. For convenience ofdescription, an ‘augmented HARQ codebook’ or ‘extended HARQ codebook’may be defined. Each of the augmented HARQ codebook or the extended HARQcodebook may include all HARQ response bits belonging to one or moreHARQ codebook(s). The augmented HARQ codebook may mean the extended HARQcodebook. In the augmented HARQ codebook, the bit string may be arrangedaccording to a preconfigured order between HARQ codebooks (e.g., HARQresponse bits). The augmented HARQ codebook may consist of HARQ responsebit(s), and the augmented HARQ codebook may be one type of HARQcodebook. One augmented HARQ codebook may correspond to one PUCCHtransmission. The augmented HARQ codebook may be generated according tomethods described below. In the following embodiments, the HARQ codebookmay be the augmented HARQ codebook, the extended HARQ codebook, or ageneral HARQ codebook. The general HARQ codebook may be an HARQ codebookrather than the augmented HARQ codebook and the extended HARQ codebook.

The terminal may not transmit the PUCCH according to the result of theLBT operation. Therefore, the terminal may still have an HARQ codebook(e.g., HARQ response) that was not transmitted. The base station may notreceive the PUCCH from the terminal. The base station may determine thereason of not detecting the PDCCH to be a case when the terminal doesnot receive the DL-DCI, a case when the terminal transmits the PUCCH butthe base station does not correctly receive the PUCCH, or a case whenthe terminal does not transmit the PUCCH according to the result of theLBT operation.

The signaling overhead for the retransmission procedure for all HARQprocesses associated with the HARQ codebook not received from theterminal may be large. Therefore, it may be preferable that the basestation transmits to the terminal information instructing to perform theretransmission procedure of the HARQ codebook. The base station maytransmit to the terminal DL-DCI including a field instructing to feedback the augmented HARQ codebook which is generated by multiplexing HARQcodebook(s) including a HARQ response for a PDSCH scheduled by theDL-DCI and a HARQ codebook (e.g., HARQ response) that may be failed tobe transmitted. The size of the augmented HARQ codebook may be changeddynamically. For example, the size of the augmented HARQ codebook may bechanged according to the number of HARQ response bits to be fed back tothe base station. The HARQ codebook (e.g., each of the HARQ codebooks)constituting the augmented HARQ codebook may mean a group of PDSCHsassociated with the corresponding HARQ codebook. The HARQ codebookincluding the HARQ response to the PDSCH scheduled by the DL-DCI mayrefer to one PDSCH group. PDSCHs corresponding to the HARQ responsebelonging to the HARQ codebook that may be failed to be transmitted maymean other PDSCH groups. Therefore, the codebook group field may be usedas a field indicating the PDSCH group.

The DL-DCI may include a codebook group field, and the codebook groupfield may be an HARQ-ACK codebook group indicator. The codebook groupfield included in the DL-DCI may instruct to feed back the augmentedHARQ codebook which is generated by multiplexing the HARQ codebookscheduled by previous DL-DCI (e.g., the HARQ codebook that may be failedto be transmitted) and the HARQ codebook (e.g., HARQ response) for thePDSCH scheduled by the corresponding DL-DCI. When the codebook groupfield has a first value, the terminal may multiplex the HARQ codebook(e.g., the HARQ codebook that includes the current HARQ response)associated with the current DL-DCI (e.g., DL-DCI including the codebookgroup field having the first value) and the previous HARQ codebook(e.g., the HARQ codebook that includes the previous HARQ response) thatmay be failed to be transmitted to generate the augmented HARQ codebook,perform an encoding operation on the augmented HARQ codebook, and mapthe encoded augmented HARQ codebooks to the PUCCH. On the other hand,when the codebook group field has a second value, the terminal mayperform an encoding operation on the HARQ codebook associated with thecurrent DL-DCI and may map the encoded HARQ codebook to the PUCCH. Theaugmented HARQ codebook may consist of only one HARQ codebook (e.g., oneHARQ response bit). Even if there is a previous HARQ codebook (e.g.,HARQ response bit) that is failed to be transmitted, the augmented HARQcodebook may not include the previous HARQ codebook (e.g., HARQ responsebit) that is failed to be transmitted.

When the number of HARQ codebooks that may be failed to be transmittedis two or more, and the codebook group field has a first value, theterminal may generate one HARQ codebook including all HARQ codebook(s)that may be failed to be transmitted (e.g., HARQ response bit(s)associated with all the HARQ process(es) that may be failed to betransmitted). An arrangement order of the previous HARQ codebook(s)(e.g., HARQ response bit(s)) in the generated HARQ codebook may be thesame as the existing arrangement order. The one HARQ codebook may begenerated by concatenating the previous HARQ codebook(s) (e.g., the HARQcodebook(s) that may be failed to be transmitted). Alternatively, theone HARQ codebook may be generated by concatenating the HARQ responsebits belonging to the previous HARQ codebook(s) (e.g., the HARQcodebook(s) that may be failed to be transmitted) in the order of HARQprocess identifiers. The previous HARQ codebook(s) may be multiplexedwith the HARQ codebook (e.g., HARQ codebook including the HARQ responseto PDSCH allocated by the current DL-DCI) associated with the currentDL-DCI to generate the augmented HARQ codebook, an encoding operationmay be performed on the augmented HARQ codebook, and the encodedaugmented HARQ codebook may be mapped to the PUCCH.

When the augmented HARQ codebook consists of the HARQ codebook(s) thatmay be failed to be transmitted, the size of the one HARQ codebook(e.g., the number of HARQ response bits) may be large. Accordingly, thebase station may transmit to the terminal information instructing toretransmit some HARQ codebooks. To support this operation, a specificfield may indicate various information.

The proposed new field (hereinafter referred to as ‘HARQ indicationfield’) may indicate one or more HARQ codebook(s) or HARQ processidentifier(s) (e.g., HARQ process numbers or HARQ process IDs). The HARQindication field may be included in a DL-DCI. The HARQ indication fieldmay consist of a plurality of bits. One bit among the plurality of bitsconstituting the HARQ indication field may indicate one or more HARQcodebook(s), one or more HARQ codebook group(s), one or more HARQprocess identifier(s), or one or more HARQ process identifier group(s).

The base station may transmit to the terminal an RRC message or a DCIincluding information indicating the above-described mapping relation(e.g., HARQ codebook, HARQ codebook group, HARQ process identifier, HARQprocess identifier group mapped to the one bit belonging to the HARQindication field). Alternatively, the base station may implicitly informthe terminal of the above-described mapping relation based on a relation(e.g., equation) defined in the technical specification withouttransmitting the separate RRC message.

Channel Access Information Field for PUCCH

The DL-DCI may include a field for information of channel access for thePUCCH transmission. The channel access information field may indicatethe type of LBT operation performed for transmission of the PUCCH. Thechannel access information field set to a first value may indicate afirst type of LBT operation. The channel access information field set toa second value may indicate a second type of LBT operation.

When the first type of LBT operation is used, the terminal may randomlyselect a backoff value within a contention window and perform a backoffoperation based on the selected backoff value. The backoff value may bedetermined by the contention window, a random variable, and/oradditional parameter(s). The additional parameter(s) may include apriority of the PUCCH (e.g., p=1). The size of the contention window maybe determined according to the priority of the PUCCH. In addition, theadditional parameter(s) may further include configuration information ofa MCOT and/or the length Td of the defer duration.

The terminal may perform a channel sensing operation (e.g., energydetection operation) in a time duration (e.g., defer duration)corresponding to the selected backoff value, and may transmit the PUCCHwhen an energy detection result is less that the energy detectionthreshold in all sensing slots belonging to the defer duration. Thesensing slot may have a length of 9 is, and the sensing slot may bedistinguished from a slot used for transmitting and receiving a signal.

When the second type of LBT operation is used, the terminal may performa channel sensing operation (e.g., energy detection operation) in allsensing slots belonging to the defer duration without a random backoffoperation. When an energy detection result is less than the energydetection threshold in all the sensing slots belonging to the deferduration, the terminal may transmit the PUCCH. Here, the length of thedefer duration may be several tens of microseconds (e.g., 25 μs or 16μs).

Meanwhile, the channel access information field may indicate three ormore values (e.g., three or more types of LBT operation). For example,the channel access information field may indicate a first value, asecond value, or a third value. The channel access information field setto the first value may indicate a first type of LBT operation. Thechannel access information field set to the second value may indicate asecond type of LBT operation. The channel access information field setto the third value may indicate a third type of LBT operation.

When the third type of LBT operation is used, the terminal may perform achannel sensing operation (e.g., energy detection operation) in allsensing slots belonging to the defer duration without a random backoffoperation. When an energy detection result is less than the energydetection threshold in all the sensing slots belonging to the deferduration, the terminal may transmit the PUCCH. Here, the length of thedefer duration may be 16 μs. For example, the length of the deferduration for the third type of LBT operation may be 16 μs, and thelength of the defer duration for the second type of LBT operation may be25 μs.

The base station may transmit to the terminal information indicating thelength of the defer duration to the terminal using higher layersignaling. The terminal may identify the length of the defer durationconfigured by the base station, and may perform the LBT operation (e.g.,the second type of the LBT operation or the third type of the LBToperation) in the defer duration.

UL-DCI Indicating Transmission of an HARQ Response

Resource allocation information of a PUCCH through which an HARQresponse for a PDSCH is transmitted may not be included in DL-DCI. Inthis case, the base station may transmit UL-DCI including a separate ULgrant for feedback of the HARQ response to the terminal. The terminalmay receive the UL-DCI from the base station, and may transmit the HARQresponse to the base station through a PUSCH indicated by the UL grantincluded in the UL-DCI. The UL-DCI may include resource allocationinformation for transmission of other signals as well as the resourceallocation information for transmission of the HARQ response. Forexample, the UL-DCI may further include resource allocation informationfor transmission of UCI (e.g., CSI reporting) and/or resource allocationinformation for transmission of a UL-SCH (e.g., transport block (TB)).The resource allocation information may be indicated by field(s)included in the UL-DCI.

Method of Explicitly Indicating a Transmission Resource of an HARQResponse

The UL-DCI may include an HARQ codebook trigger field, and the HARQcodebook trigger field may instruct the terminal to feed back an HARQresponse. When the HARQ codebook trigger field is set to a first value,the terminal may generate one HARQ codebook including HARQ responses forall HARQ processes. The number of bits included in the HARQ codebook maybe the same as the number of HARQ processes configured by higher layersignaling. When the HARQ codebook trigger field is set to a secondvalue, the terminal may not map the HARQ response to a PUSCH.

Alternatively, the HARQ codebook trigger field included in the UL-DCImay consist of a plurality of bits. The HARQ codebook trigger field mayindicate HARQ codebook(s) and/or HARQ process identifier(s). One bitbelonging to the HARQ codebook trigger field may indicate that feedbackof one or more HARQ codebooks, one or more HARQ codebook groups, one ormore HARQ process identifiers, or one or more HARQ process identifiergroups is requested. Another bit belonging to the HARQ codebook triggerfield may instruct the terminal not to map the HARQ response to thePUSCH.

The base station may transmit to the terminal an RRC message indicatingthe above-described mapping relation (e.g., mapping relations betweenone bit and ‘the HARQ codebook(s), HARQ codebook group(s), HARQ processidentifier(s), or HARQ process identifier group(s)’). Alternatively, theterminal may identify the above-described mapping relation based on arelation (e.g., equation) defined in the technical specification withoutreceiving the RRC message. A code block group transmission information(CBGTI) included in the UL-DCI may be used to indicate transmission ofthe HARQ response. In this case, the UL-DCI may not include resourceallocation information of the UL-SCH and may include resourceinformation of a PUSCH for transmission of UCI (e.g., HARQ response,CSI).

Method of Implicitly Indicating a Transmission Resource of an HARQResponse

The UL-DCI may not include the field explicitly requesting transmissionof an HARQ response (e.g., HARQ feedback). However, the transmissionrequest of the HARQ response may be implicitly indicated by acombination of fields included in the UL-DCI.

In a proposed method, when the UL-DCI received from the base stationdoes not include a field indicating a transmission resource of a UL-SCH,and a downlink assignment index (DAI) field included in thecorresponding UL-DCI is set to a specific value (e.g., a value otherthan ‘00’), the terminal may determine that the corresponding UL-DCIrequests the feedback of the HARQ response.

Alternatively, the terminal receiving the UL-DCI may interpret that theCBGTI for the UL-SCH indicates an index of the HARQ codebook group. Thisoperation may be applied when CBG transmission is configured in theterminal by an RRC message. Alternatively, the terminal may interpretthat the DAI field included in the UL-DCI indicates the index of theHARQ codebook group.

Method of Performing Feedback of an HARQ Response in Consideration of aNew Feedback Indicator (NFI) and/or a New Data Indicator (NDI)

The terminal may not receive a PDCCH according to a result of the LBToperation at the base station due to characteristics of an unlicensedband. In addition, the terminal may not transmit the PUCCH according toa result of the LBT operation. Therefore, the number of bits of the HARQresponse predicted by the base station may be different from the numberof bits of the HARQ response transmitted by the terminal. To solve thisproblem, the DL-DCI may include an NFI for a PDSCH group (or HARQcodebook). The size of the NFI may be 1 bit. When the PUCCH is receivedfrom the terminal, the base station may change the value of the NFI forthe HARQ codebook (or group identifier (GID)) included in the PUCCH toanother value. When the value of the NFI received from the base stationis changed, the terminal may determine that HARQ responses for all HARQprocess identifiers (HPIDs) belonging to a GID associated with thecorresponding NFI have been received at the base station.

The base station may transmit the NDI for the HARQ process to theterminal. The size of the NDI may be 1 bit. The terminal may receive theNDI from the base station, and may determine whether transmission of theDL-SCH associated with the NDI is initial transmission orretransmission. Accordingly, the terminal may determine whether toperform a soft combining operation in a decoding procedure of theDL-SCH. The base station may generate DCI including one or more of theDAI, NFI, NDI, and GID, and may transmit the generated DCI to theterminal. The terminal may receive the DCI from the base station, andmay identify the information included in the DCI.

In a proposed method, the value of the HARQ response may be identifiedbased on the NFI associated with the HARQ process. Here, the HARQresponse may be NACK. Alternatively, the HARQ response may be ACK orNACK, which is a decoding result for the DL-SCH.

The terminal may know in advance the NFI and NDI for the HPID, and mayreceive the DL-DCI from the base station. The DL-DCI may be received ata time point t (e.g., slot t), and the terminal may compare each of theNFI and NDI included in the DL-DCI with each of the NFI and NDI whichare already known. The terminal may identify whether each of the NFI andthe NDI is changed based on the comparison result. For example, theterminal may compare each of NFI and NDI included in a DL-DCI receivedat a time point r before the time point t with the NFI and NDI includedin the DL-DCI received at the time point t. Here, the DL-DCI received atthe time point r and the DL-DCI received at the time point t may havethe same GID.

Meanwhile, the terminal may not know a reference value of the NFI. Forexample, when the base station initially transmits the DL-DCI for theHPID and the GID at the time point t (that is, there is no DL-DCIreceived before the time point t), the terminal may not know thereference value of the NFI. When it is determined that the NFI ischanged, the terminal may know a GID x to which the HPID indicated bythe DL-DCI received at the time point t (e.g., slot t) belongs last orthe GID x at the time point t.

The DL-DCI received in the slot t may indicate that the correspondingHPID belongs to a GID y. x may be equal to y. Alternatively, x may bedifferent from y. Regarding all HPIDs belonging to the GID x, it may beassumed that the terminal knows all HARQ responses transmitted at a timepoint s (e.g., s≠t) when the terminal transmits its HARQ response. Theterminal may further transmit an HARQ response for the correspondingHPID in the slot t to the base station.

On the other hand, when the NFI included in the DL-DCI received at thetime point t is the same as the NFI received before the time point t,the terminal may interpret that the base station has not successfullyreceived the PUCCH associated with the corresponding GID at the timepoint s. The base station may not know HARQ responses of all HPIDsbelonging to the corresponding GID. The terminal may transmit the HARQresponse for the corresponding HPID to the base station at the timepoint t, and may also transmit HARQ response(s) for other HPID(s)belonging to the GID to the base station. The HARQ response(s) for otherHPID (s) belonging to the corresponding GID may be transmitted at thetime point t.

In a proposed method, the HARQ response to the HARQ process may beidentified based on the NFI and the NDI. The HARQ response may berepresented by NACK. Alternatively, the HARQ response may be representedby ACK or NACK.

The terminal may receive the DL-DCI at the time point t, and mayidentify the NFI and NDI based on the DL-DCI. The terminal may identifywhether the NDI is changed by comparing the NDI included in the DL-DCIreceived at a time point (e.g., time point t-1) before the time point tand the NDI included in the DL-DCI received at the time point t. Here,the HPID associated with the DL-DCI received at a time point before thetime point t may be the same as the HPID associated with the DL-DCIreceived at the time point t. When the DL-DCI is not received before thetime point t, the terminal may not know the reference value of the NDI.It may be difficult for the terminal to determine whether to perform asoft combining operation for the corresponding HPID.

Based on the DL-DCI received at the time point t, it may be identifiedthat the NFI is changed and the NDI is not changed. In this case, thetransmission operation of the DL-SCH may be meaningless. That is, thebase station may change the NFI since the base station has received theHARQ response for the HPID, and it may be represented by the DL-DCI(e.g., the DL-DCI transmitted at the time point t) that the transmissionresource for a new DL-SCH is not allocated. Therefore, the terminal maynot need to transmit the HARQ response, and the base station may notneed to receive the HARQ response.

However, in a case other than the case described above (e.g., when theNDI is changed regardless of the NFI or when the NFI and NDI do notchange), the terminal may transmit the HARQ response for the DL-SCHassociated with the corresponding HPID.

The above-described exemplary embodiments may be applied to when the DCIassociated with the HPID is not received at the time point t or when theDCI associated with the HPID is received at a time point (e.g., timepoint t-1) before the time point t. The NFI for the HPID may beidentified based on the DCI received at the time point t. This isbecause the HPID and the GID to which the HPID belongs (e.g., GID y) areindicated by the DL-DCI, and the NFI for the GID is indicated.

Based on the above description, the terminal may identify the change ofthe NFI for the GID to which the corresponding HPID belongs last or theGID to which the HPID currently belongs based on the DCI received at thetime point t or a time point before the time t. The terminal mayidentify whether the NFI is changed at a time point e or a time pointbefore the time point e. Here, it may be defined as ‘e≤t’. In addition,the terminal may identify whether the NDI is changed at the point time eor a time point before the time point e. When the NDI is not changed,the terminal may determine that a new DL-SCH is not initiallytransmitted. The base station may not need to receive an HARQ responsefor the corresponding HPID. When the NDI is changed, the terminal maydetermine that a new DL-SCH is initially transmitted and may transmitthe HARQ response for the corresponding HPID to the base station.

The time at which the HARQ response associated with the GID x to whichthe HPID belongs is transmitted may be referred to as s, and the time atwhich the DL-DCI including the changed NDI is received after thetransmission of the HARQ response may be referred to as q. In this case,‘s≤q≤t’ may be defined. Regarding the GID x to which the HPID belongs,the time point when the change of the NFI is recognized may be referredto as e. In this case, ‘s≤e≤t’ may be defined.

A case when the terminal feeds back the HARQ response to the HPID or acase when the terminal feeds back a predefined value (e.g., ACK or NACK)or an arbitrary value may be considered. When e is after s and q isafter s, the terminal may feed back the HARQ response to the basestation. Here, e may be equal to q. In cases other than the casedescribed above, the terminal may feed back a NACK, a predefined value,or an arbitrary value to the base station. In a proposed method, theterminal may perform an encoding operation on the HARQ responses for allHPIDs configured by higher layer signaling regardless of the NFI and theNDI, and may transmit the encoded HARQ response to the base station.

On the other hand, when all DL-DCIs associated with all HPIDs belongingto the GID are not received from the base station, the terminal may notknow whether the NFI is changed. This operation may be for a case whenthe DL-DCI for the GID is not transmitted from the base station or acase when the terminal fails to decode all the DL-DCIs for the GID. Inthis case, the terminal may not know that the NFI is changed. This casemay rarely occur.

Information Included in DCI Indicating Transmission of an HARQ Response

In a proposed method, DCI (e.g., DL-DCI or UL-DCI) may include NFIs forall GIDs. The terminal may directly identify the NFI for the GID fromthe DCI. Therefore, the terminal may know the change of the NFI for anarbitrary HPID. When the NFI is changed, the terminal may observe thechange of the NDI associated with the corresponding HPID. When the NDIis not changed, the terminal may not need to transmit the HARQ responsefor the corresponding HPID. Accordingly, the terminal may map apredefined value (e.g., NACK or ACK) or an arbitrary value to an uplinkchannel as the HARQ response for the corresponding HPID. The basestation may not need to identify the HARQ response for the HPID.

In another proposed method, the DCI (e.g., DL-DCI or UL-DCI) may includeonly configuration information for transmission of the HARQ response.That is, the DCI may not include other information (e.g., NFI and/orNDI) than configuration information for transmission of the HARQresponse.

HARQ Response and Additional Information in an HARQ Response FeedbackProcedure

In a proposed method, the terminal may perform an encoding operation onHARQ responses (e.g., ACK, NACK) for all HPIDs configured by higherlayer signaling, and may transmit the encoded HARQ responses to the basestation.

For example, the base station may transmit an RRC message includingconfiguration information of a type2 codebook and configurationinformation of a type3 codebook to the terminal. The terminal mayreceive the RRC message from the base station, and may identify theconfiguration information of the type 2 codebook and the configurationinformation of the type 3 codebook included in the RRC message. The type2 codebook may be the above-described augmented HARQ codebook orextended HARQ codebook. The type 2 codebook may be an enhanced dynamiccodebook. The type 2 codebook may include one or two HARQ response bits(e.g., HARQ codebooks). In the type 2 codebook, the HARQ response bitsmay be arranged according to the PDSCH order (e.g., combination of oneor more of reception order, scheduling order, order of start symbol, andorder of end symbol). For example, the HARQ response bits may bearranged first according to the order of time resources of the PDSCH,and then HARQ response bits may be arranged according to the order offrequency resources of the PDSCH.

The type 3 codebook may be a semi-static codebook. The type 3 codebookmay include a plurality of HARQ response bits (e.g., HARQ codebooks). Inaddition, the type 3 codebook may further include NDIs as well as theplurality of HARQ response bits. In embodiments, the HARQ codebookincluding ‘HARQ response bit and NDI’ may mean the type 3 codebook.Alternatively, the HARQ codebook including the HARQ response bit withoutthe NDI may be interpreted as the type 3 codebook. In the type 3codebook, the plurality of HARQ response bits may be arranged accordingto the order of HARQ process numbers. For example, the plurality of HARQresponse bits may be arranged first according to the order of HARQprocess numbers, and then the plurality of HARQ response bits may bearranged according to the order of frequency resources of the PDSCH.

The base station may transmit the DL-DCI including a field triggeringthe type 3 codebook to the terminal. The size of the field that triggersthe type 3 codebook may be 1 bit. When the field triggering the type 3codebook is set to the first value, the corresponding field may triggertransmission of the type 3 codebook. When the field triggering the type3 codebook is set to the second value, the corresponding field may nottrigger the transmission of the type 3 codebook, but instead indicatesthe transmission of any indicated codebook such as the type 1 codebookor the type 2 codebook. That is, when the field triggering the type 3codebook is set to the first value, the terminal may generate the type 3codebook and transmit the type 3 codebook to the base station. When thefield that triggers the type 3 codebook is set to the second value, theterminal may generate the type 1 or 2 codebook and transmit the type 1or 2 codebook to the base station.

Meanwhile, when some of DL-DCIs are not received from the base station,the terminal may interpret bits of an HARQ response for a specific HARQprocess as an existing value rather than a updated value because theterminal does not receive PDSCH. The terminal may not receive DL-DCIincluding a toggled NDI. Because the terminal has not received the PDSCHassociated with the HARQ process indicated by the DL-DCI, the terminalmay not be able to decode the TB. Therefore, the terminal may maintain astored state of the HARQ response associated with the HARQ processindicated by the DL-DCI. That is, the state of the HARQ process known tothe base station may be different from the state of the HARQ processknown to the terminal.

Thereafter, the base station may transmit to the terminal informationinstructing to transmit HARQ responses (e.g., HARQ codebook(s)) for theconfigured all HARQ processes in a PUCCH or a PUSCH. In this case, thebase station may misunderstand the HARQ response of the correspondingHARQ process. In order to solve this problem, in the feedback procedureof the HARQ response, the terminal may transmit additional informationas well as the HARQ response to the base station.

In a proposed method, the NDI corresponding to the HPID may betransmitted together with the HARQ response. The HARQ process maycorrespond one-to-one with the NDI. The terminal may concatenate a bitstring of the last NDI for the corresponding HARQ process with a bitstring of the HARQ response. Here, the bit string of the HARQ responsemay be concatenated with the bit string of the NDI. Alternatively, thebit string of the HARQ response may be concatenated with the bit stringof the NDI, and the concatenated bit strings may be concatenated withthe HPID. The terminal may perform an encoding operation on theconcatenated bit strings and transmit the encoded bit strings to thebase station.

In another proposed method, the terminal may transmit the NFI for eachGID. The GID may mean the PDSCH group, and may correspond to the HARQcodebook index. For example, the terminal may concatenate the bit stringof the HARQ response and the bit string of the NFI. Here, the bit stringof the HARQ response may be concatenated with the bit string of the NFI.Alternatively, with respect to the GID, the bit string of the NFI may beconcatenated with the bit string of the HARQ response, and then theconcatenated bit strings may be concatenated with the GID. The terminalmay perform an encoding operation on the concatenated bit strings andtransmit the encoded bit strings to the base station. The HARQ responsesassociated with some HARQ processes may be transmitted together with theNDI.

According to the above-described methods, the terminal may transmit theHARQ response and NDI associated with the HARQ process or the HARQresponse associated with the HARQ process. The case when the HARQresponses associated with all HARQ processes are transmitted or the casewhen the HARQ responses and NDIs associated with all HARQ processes aretransmitted may not be preferable. The reason is that there is a case inwhich the NDI toggle is hard to be applied to a specific HARQ process.For example, the base station may not transmit resource allocationinformation of the DL-SCH associated with the corresponding HARQprocess. Alternatively, the base station may instruct the terminal tofeed back the HARQ response at a timing when the HARQ response for thecorresponding HARQ process cannot be processed (e.g., when a timecorresponding to N1 symbols is not passed from the reception time pointof the DL-SCH). In this case, since the terminal cannot derive a validHARQ response, the base station may ignore the HARQ response for thecorresponding HARQ process. The HARQ response and/or the NDI for thecorresponding HARQ process may be unnecessary. When the characteristicsof the HARQ process are shared between the base station and theterminal, unnecessary information may be omitted in the feedbackprocedure of the HARQ response.

In the feedback procedure of the HARQ response, the last PDSCH may bedetermined to correspond to an un-updated HARQ response bit (i.e., theHARQ response bit for the scheduled PDSCH before the last PDSCH) for agiven HARQ process according to the processing capability (e.g., thetime required to process the PDSCH, or N1 symbols indicated by the RRCsignaling) of the terminal. Regarding the HARQ response bit for thegiven HARQ process corresponding to the last PDSCH and the PDSCH beforethe last PDSCH, the HARQ response bit may be transmitted to the basestation together with the NDI. There may be some HARQ processes whoseinformation such as an updated HARQ response bit and/or an updated NDIis not reflected to the HARQ codebook, and for those HARQ processesuseful information may not be transmitted to the base station. In thegeneration procedure of the HARQ codebook, the terminal may fit theentire length of the HARQ codebook using a preconfigured value (e.g.,NACK, ‘0’) shared between the base station and the terminal.

Method of Not Distinguishing Between Active and Inactive Carriers

Without discrimination between an activated carrier and a deactivatedcarrier, the terminal may feed back the HARQ response. A DCI, a MAC CE,or an expiration of a timer may indicate that the carrier is activatedor deactivated, and the size of the HARQ codebook may be determined byan RRC signaling. Accordingly, the terminal may feed back the HARQcodebook (e.g., HARQ response) having the same size to the base stationwithout depending on the DCI. In a specific carrier, the HARQ responsemay be transmitted together with the NDI. Therefore, the number of HARQprocesses may be twice the number of existing HARQ processes.

Since the base station does not transmit a PDSCH on the deactivatedcarrier, the HARQ response and the NDI may not be useful values at thebase station. Since the DCI, the MAC CE, or the expiration of the timerindicates that the carrier is activated or deactivated, and the size ofthe HARQ codebook is determined by an RRC signaling, the terminal maytransmit NACK as the HARQ response on the deactivated carrier. The NDImay be set to a preconfigured value (e.g., ‘0’) or to an arbitraryvalue.

Method of Distinguishing Between Active and Inactive Carriers

The activated carrier may be distinguished from the deactivated carrierand the HARQ response may be fed back. Since the base station does notperform a scheduling operation in the deactivated carrier, transmissionof the HARQ response and the NDI may be unnecessary. Therefore, the sizeof the UCI in the deactivated carrier may be reduced.

In a proposed method, the terminal may feed back an HARQ response in theactivated carrier. That is, the terminal may not generate an HARQresponse in the deactivated carrier. HARQ responses may be generated forall HARQ processes. Alternatively, the HARQ response may be transmittedtogether with the NDI. That is, an HARQ response block (e.g., HARQcodebook) may include the HARQ response and the NDI. In the followingembodiments, the HARQ response block may mean the HARQ codebookincluding the HARQ response bit and the NDI associated with thecorresponding HARQ response bit. Here, an arrangement order and/or aconcatenation order of the HARQ response and the NDI in the HARQresponse block may be determined according to a preconfigured rule(e.g., scheduling order, order of the HARQ process identifier). Thearrangement order and/or concatenation order of the HARQ response andthe NDI in the HARQ response block may be shared in advance between thebase station and the terminal. In this case, a signaling procedure forinforming the arrangement order and/or concatenation order of the HARQresponse and the NDI may be unnecessary.

In another proposed method, the terminal may generate an HARQ responseblock including the HARQ response and the NDI in an activated carrier.The terminal may generate an HARQ response block including only an HARQresponse in a deactivated carrier. Here, the arrangement order and/orthe concatenation order of the HARQ response and the NDI in the HARQresponse block may be determined according to a preconfigured rule. Thearrangement order and/or the concatenation order of the HARQ responseand the NDI in the HARQ response block may be shared in advance betweenthe base station and the terminal. In this case, signaling for informingthe arrangement order and/or the concatenation order of the HARQresponse and the NDI may be unnecessary. The terminal may reduce thesize of each HARQ response and NDI included in the HARQ response block.Thus, a polar coding rate may be reduced, and an error rate at the basestation may be reduced.

Method of Generating an HARQ Response

The following embodiments may be applied to the type 3 codebook. Thatis, in the following embodiments, the HARQ codebook may mean the type 3codebook. A DCI scheduling a PDSCH or a PUSCH may include informationinstructing to transmit HARQ responses for all HARQ processes. Theterminal may map HARQ responses (e.g., HARQ codebooks or HARQ responsebits) for all HARQ processes to an uplink channel in all carriersconfigured by an RRC signaling. The HARQ responses for all HARQprocesses may be arranged in a preconfigured order (e.g., schedulingorder or order of the HARQ process identifier). For example, in the HARQcodebook, the HARQ response bits may be arranged according to thescheduling order of the data channel (e.g., PDSCH) associated with thecorresponding HARQ response bits.

Method of Generating an HARQ Response (e.g., HARQ Codebook) in aPreconfigured Carrier

The following embodiments may be applied to the type 3 codebook. Thatis, in the following embodiments, the HARQ codebook may mean the type 3codebook. The size of the HARQ codebook may be configured by an RRCsignaling. According to a time domain resource allocation (TDRA) indexand K1 configured by an RRC signaling, an arrangement order of bits inthe HARQ codebook may be according to an assignment order of PDSCHs. Thesize of the HARQ codebook may be independent of the number of HARQprocesses. The number of HARQ processes may be greater than the numberof bits in the HARQ codebook. According to the conventional method, itmay be difficult to arrange bits of the HARQ responses for all HARQprocesses in one HARQ codebook within a preconfigured carrier.

In a proposed method, the terminal may generate the HARQ codebook byarranging the HARQ responses according to HARQ process identifier (e.g.,HARQ process numbers (HPNs), HPIDs) in the preconfigured carrier. Forexample, when there are x HARQ processes, x HARQ response bits may bearranged in the HARQ codebook in the order of the x HARQ processes. Thisoperation may be independent of the TDRA index configured in theterminal.

The base station may transmit to the terminal information instructing togenerate a separate HARQ codebook having a semi-static size. In thiscase, methods for generating the HARQ codebook may be different. Evenwhen the HARQ codebook is simply generated according to theabove-described methods, the HARQ codebook may be generated according totwo or more schemes.

The HARQ codebook may be generated in one scheme. One HARQ codebook mayinclude two or more HARQ partial codebooks. The HARQ partial codebooksmay have characteristics according to the conventional scheme (e.g.,characteristics determined by the TDRA). When the transmission timepoint K1 of the HARQ codebook is a non-numerical value for the HARQprocess, a maximum of 1 bit may be added to the HARQ codebook.

In a proposed method, the terminal may concatenate the HARQ partialcodebooks in a preconfigured carrier. When there are HARQ process(es)not belonging to the HARQ partial codebook, the terminal may generate anHARQ codebook including the concatenated HARQ partial codebooks andbit(s) preconfigured for the corresponding HARQ process(es). Here, theHARQ partial codebooks included in the HARQ codebook may be generatedbased on the conventional scheme.

For example, the number of HARQ processes may be x, and the number ofHARQ partial codebooks may be two or more. One HARQ process may notnecessarily belong to a specific HARQ partial codebook. The size of theHARQ partial codebook may be determined based on the TDRA and additionalbit(s) (e.g., ‘0’ or ‘1’) indicated by higher layer signaling.Therefore, the base station and the terminal may know the size of eachof the HARQ partial codebooks. The HARQ codebook may include theconcatenated HARQ partial codebooks. The HARQ codebook may also includeHARQ responses useful at the base station. Even when there are HARQprocess(s) not belonging to the HARQ partial codebook, the terminal maygenerate the HARQ codebook according to the number of all HARQprocesses. Accordingly, the terminal may append a value(s) (e.g., NACK)preconfigured between the base station and the terminal to the HARQcodebook.

When carrier aggregation is configured, the base station may activateand deactivate specific carrier(s). The carrier may have one or morebandwidth parts (BWPs). The base station may activate one BWP among theone or more BWPs. In the active BWP, the TDRA may be determined by anRRC signaling. According to the conventional scheme, one BWP (e.g.,firstActiveDownlinkBWP) among the BWPs may be a reference to generatethe HARQ codebook including the HARQ response in the deactivatedcarrier.

In a proposed method, when the carrier is deactivated, the HARQresponses may be arranged in the order of the HARQ process identifier(e.g., HARQ process IDs or HARQ process numbers) irrespective of the BWP(e.g., regardless of the TDRA). The base station may not assign a PDSCHin the deactivated carrier. Therefore, the HARQ codebook may includeonly NACK. In a proposed method, the terminal may generate an HARQresponse block including HARQ response(s) and NDI(s) in all carriers,and may map the HARQ response block to a PUCCH or a PUSCH.

In another proposed method, the terminal may generate an HARQ responseblock including an HARQ response and an NDI in an activated carrier, andthe terminal may generate an HARQ response block including only an HARQresponse (e.g., NACK) in a deactivated carrier. That is, the HARQresponse block in the deactivated carrier may not include the NDI.

Method of Arranging NDIs and HARQ Responses

The following embodiments may be applied to the type 3 codebook. Thatis, in the following embodiments, the HARQ codebook may mean the type 3codebook. An arrangement order of bit strings of HARQ responses in acarrier may be determined. The terminal may generate an HARQ codebook byconcatenating bit strings of HARQ responses based on an order ofcarriers (e.g., serving cell indexes).

In a proposed method, a bit string of HARQ responses and a bit string ofNDIs may be generated for each carrier, and the terminal may generate anHARQ codebook by concatenating the bit string of the HARQ responses withthe bit string of the NDIs. For the arrangement of the HARQ responsesand the NDIs, a conventional HARQ codebook generation scheme or anarrangement scheme according to HPNs may be used. This operation mayalso be applied to a carrier in which the NDI is not used. For example,the terminal may generate an HARQ codebook based on a scheme describedin Table 6 below.

TABLE 6 1. For CC index =0,1,2,... A. Generate a bit string of HARQresponses B. Generate a bit string of NDIs C. Concatenate the bit stringof HARQ responses with the bit   string of NDIs 2. Concatenate the bitstrings obtained for the respective CCs

Alternatively, the terminal may generate an HARQ codebook based on ascheme described in Table 7 below. A generation scheme of an HARQcodebook in an activated carrier may be different from a generationscheme of an HARQ codebook in a deactivated carrier.

TABLE 7 1. For CC index =0,1,2,... A. Generate a bit string of HARQresponses B. Generate a bit string of NDIs for an activated carrier,  and omit generation of a bit   string of NDIs for an deactivatedcarrier C. Concatenate the bit string of HARQ responses with the bit  string of NDIs 2. Concatenate the bit strings obtained for therespective CCs

In another proposed method, the HARQ response and the NDI for the HARQprocess may be configured in a bit pair. [HARQ response, NDI], which isa bit pair in a carrier, may be arranged according to the conventionalHARQ codebook generation scheme or the arrangement scheme according toHPNs. That is, the conventional HARQ codebook generation scheme orarrangement scheme according to HPNs may be applied on a bit pair basis.This operation may be applied to a method of generating an HARQ responseblock including HARQ responses and NDIs for all HARQ processes. Forexample, the terminal may generate the HARQ codebook based on a schemedescribed in Table 8 below. In a deactivated carrier, the HARQ responseblock may consist of only HARQ responses instead of bit pairs.

TABLE 8 1. For CC index =0,1,2,... A. Generate a bit string of [HARQresponse, NDI]s 2. Concatenate the bit strings obtained for therespective CCs

Alternatively, the terminal may generate an HARQ codebook based on ascheme described in Table 9 below. A generation scheme of an HARQcodebook in an activated carrier may be different from a generationscheme of an HARQ codebook in a deactivated carrier.

TABLE 9 1. For CC index =0,1,2,... A. Generate a bit string of [HARQresponse, NDI]s for an   activated carrier, and   generate a bit stringof HARQ responses for a deactivated carrier 2. Concatenate the bitstrings obtained for the respective CCs

In another proposed method, bit strings of HARQ responses for allcarriers may be arranged and bit strings of NDIs for all carriers may bearranged. Thereafter, the bit strings of the HARQ responses may beconcatenated with the bit strings of the NDIs. This operation may beperformed according to the conventional HARQ codebook generation schemeor the conventional arrangement scheme according to HPNs. Theconventional HARQ codebook generation scheme or the conventionalarrangement scheme according to HPNs may also be applied to a carrier inwhich NDI is omitted. For example, the terminal may generate an HARQcodebook based on a scheme described in Table 10 below.

TABLE 10 1. For CC index =0,1,2,... A. Generate a bit string of HARQresponses 2. Concatenate the bit strings of the HARQ responses obtainedfor the respective CCs 3. For CC index =0,1,2,... A. Generate a bitstring of NDIs 4. Concatenate the bit strings of the NDIs obtained forthe respective CCs 5. Concatenate the bit strings of the HARQ responseswith the bit strings of the NDIs

For example, the terminal may generate an HARQ codebook based on ascheme described in Table 11 below.

TABLE 11 1. For CC index =0,1,2,... A. Generate a bit string of HARQresponses 2. Concatenate the bit strings of HARQ responses obtained forthe respective CCs 3. For CC index =0,1,2,... B. Generate a bit stringof NDIs for an activated carrier 4. Concatenate the bit strings of theNDIs obtained for the respective CCs 5. Concatenate the bit strings ofthe HARQ responses with the bit strings of the NDIs

UL-DCI Indicating PUCCH Transmission

The UL-DCI may include a field indicating PUCCH transmission. Theterminal may transmit UCI (e.g., CSI or HARQ response) on a PUCCH basedon the field included in the UL-DCI.

The UL-DCI may include a field indicating CSI reporting (hereinafter,referred to as CSI report field'). The CSI report field may consist ofone or more bits. One bit included in the CSI report field maycorrespond to one or more CSI reports. One CSI report may be acombination of one or more of channel quality information (CQI),precoding matrix indicator (PMI), CSI-RS resource indicator (CRI),SS/PBCH resource block indicator (SSBRI), layer indicator (LI), rankindicator (RI), and L1 reference signal received power (L1-RSRP).

The UL-DCI may include a field indicating a report of HARQ response(hereinafter, referred to as ‘HARQ report field’). The HARQ report fieldmay consist of one or more bits. One bit included in the HARQ reportfield may correspond to one or more HARQ codebooks (e.g., HARQresponses). One HARQ codebook may consist of one or more HARQ responsebits. The base station and the terminal may know in advance a mappingrelation between the HARQ response bit(s) included in the HARQ codebookand the HARQ process identifier.

Upon receiving the UL-DCI, the terminal may identify transmissionresources of a PUSCH based on the information elements included in thecorresponding UL-DCI, and may determine whether to multiplex the UCI anda UL-SCH. The terminal may transmit the UCI and the UL-SCH using asingle channel (e.g., PUSCH) by multiplexing the UCI with the UL-SCH.When the UCI is not multiplexed with the UL-SCH, the terminal maytransmit the UCI on a PUCCH and may transmit the UL-SCH on a PUSCH.Here, the PUCCH and the PUSCH may be located in the same symbol, and afrequency resource of the PUCCH may be different from a frequencyresource of the PUSCH. Therefore, a power backoff applied to a poweramplifier of the terminal may increase, and thus an uplink coverage maydecrease.

In order to satisfy the frequency regulation in the communication systemoperating in a shared spectrum, each of the PUSCH and the PUCCH may beconfigured in form of an interlace. This operation may mean that thePUSCH is multiplexed with the PUCCH in the frequency domain. Also inthis case, a power backoff may be required in the power amplifier of theterminal. In a shared spectrum, a channel to which the UCI is mapped maybe different from a channel to which the UL-SCH is mapped. The UCI maybe transmitted on a PUCCH and the UL-SCH may be transmitted on a PUSCH.

UL-DCI Including a PUCCH Resource Index (PRI)

The UL-DCI may include a field indicating a PRI (hereinafter, referredto as ‘PRI field’). When the UCI consists of 1 bit or 2 bits, a PUCCHresource may be determined by an index of a CCE to which the UL-DCI ismapped as well as the PRI indicated by the UL-DCI. When the UCI isconfigured with three or more bits, the PUCCH resource may be determinedbased on the number of bits of the UCI and the PM indicated by theUL-DCI. Here, the PUCCH resource may be symbol(s) occupied by the PUCCHin a slot of the time domain. The slot in which the PUCCH is transmittedmay mean a slot indicated by the resource allocation information of thePUSCH included in the UL-DCI.

An MCS level applied to the UCI may vary depending on the size of theUCI. Since a channel encoding scheme varies according to the size of theUCI, the MCS level applied to the UCI may vary. When the size of the UCIis less than 3 bits, a first MCS level may be applied to the UCI. Whenthe size of the UCI is 3 bits or more and less than 12 bits, a secondMCS level may be applied to the UCI. When the size of the UCI is 12 bitsor more, a third MCS level may be applied to the UCI.

The base station may configured the MCS level applied to the UCI to theterminal using higher layer signaling. Accordingly, the terminal may mapthe UCI to the PUCCH using the MCS level configured by higher layersignaling. Alternatively, the base station may transmit UL-DCI includinginformation indicating the MCS level applied to the UL-SCH to theterminal. The terminal may derive the MCS level applied to the UCI byapplying an offset to the MCS level indicated by the UL-DCI. Here, theoffset may be indicated by the corresponding UL-DCI. Alternatively, theoffset may be configured by higher layer signaling. The offset appliedto the MCS level in the NR communication system may be different foreach type of UCI. For example, the offset may be defined asbetaOffsetACK, betaOffsetCSI-Part1, or betaOffsetCSI-Part2 according tothe type of UCI.

Meanwhile, UL-DCI may include a UL-SCH indicator, and the UL-SCHindicator may indicate whether the UL-SCH is mapped to the PUSCH. Whenthe UL-SCH indicator indicates that the UL-SCH is not mapped to thePUSCH, the terminal may transmit only the PUCCH. On the other hand, whenthe UL-SCH indicator indicates that the UL-SCH is mapped to the PUSCH,the terminal may transmit the PUSCH and the PUCCH in the same slot. Thetime resource of the PUCCH indicated by the PRI may overlap with thetime resource of the PUSCH indicated by the UL-DCI. Alternatively, thetime resource of the PUCCH indicated by the PM may not overlap with thetime resource of the PUSCH indicated by the UL-DCI.

When the time resource of the PUCCH overlaps with the time resource ofthe PUSCH, the base station may configure the frequency resource of thePUCCH to be different from the frequency resource of the PUSCH, and maytransmit frequency resource information of each of the PUCCH and thePUSCH to the terminal. That is, the frequency resource indicated by thefrequency resource information of the PUCCH may be different from thefrequency resource indicated by the frequency resource information ofthe PUSCH. An LBT subband in which the PUCCH is transmitted may beincluded in an LBT subband(s) in which the PUSCH is transmitted.Frequency resources corresponding to the interlace of the PUCCH in theLBT subband in which the PUCCH is transmitted may be different fromfrequency resources corresponding to the interlace of the PUSCH.

It may be defined in the technical specification that the operation oftransmitting only the PUCCH based on the UL-DCI is not supported. Whenthe UL-DCI indicates not to map the UL-SCH to the PUSCH, the terminalmay ignore the PRI field included in the corresponding UL-DCI.

Method of Transmitting UCI When Multiple PUSCHs are Assigned

The base station may transmit one UL-DCI including resource allocationinformation of two or more UL-SCHs (e.g., PUSCHs) to the terminal. Thisoperation may be performed when there is a lot of UL data in theterminal. According to this operation, a transmission successprobability of UL data may increase.

A format of the UL-DCI including resource allocation information of aplurality of PUSCHs may be distinguished from a format of the UL-DCIincluding resource allocation information of one PUSCH. The base stationmay inform the terminal of the format of the UL-DCI including theresource allocation information of a plurality of PUSCHs and/or theformat of the UL-DCI including the resource allocation information ofone PUSCH using higher layer signaling. According to the configurationof the base station, the terminal may perform a search operation for twoor more UL-DCI formats in one search space. In this case, one or moreUL-DCIs may be mapped to the same search space.

In a PUSCH assignment procedure, the base station may transmitinformation indicating multiplexing of the UCI (e.g., CSI or HARQresponse) and the UL-SCH to the terminal. Alternatively, in theassignment procedure of the PUSCH, the base station may transmit to theterminal information instructing to transmit the UCI (e.g., CSI or HARQresponse) in the PUCCH and to transmit the UL-SCH in the PUSCH. Here,the PUCCH and the PUSCH may be FDMed in the same symbol.

The base station may transmit position information of the PUSCH in whichthe UCI is multiplexed with the UL-SCH (e.g., the k-th PUSCH among theplurality of PUSCHs allocated by the UL-DCI) to the terminal.Alternatively, the position information of the PUSCH in which the UCI ismultiplexed with the UL-SCH may be defined in the technical standard. kmay be a natural number.

Regardless of the type of the UCI, a field indicating the positioninformation of the PUSCH in which the UCI is multiplexed with the UL-SCHmay be included in the UL-DCI. Alternatively, the field indicating theposition information of the PUSCH in which the UCI is multiplexed withthe UL-SCH may be configured differently according to the type of thecorresponding UCI. For example, the PUSCH to which the HARQ response ismapped may be different from the PUSCH to which the CSI is mapped. Inthis case, the UL-DCI may include a field indicating a time resource ofan HARQ response (e.g., a PUSCH to which the HARQ response is mapped)and a field indicating a time resource of the CSI (e.g., a PUSCH towhich the CSI is mapped). The field indicating the time resource of theHARQ response may be distinguished from the field indicating the timeresource of the CSI.

Method for the Base Station to Inform a Time Resource to Which UCI isMapped

In a proposed method, UL-DCI may include a field (hereinafter, referredto as ‘UCI mapping indication field) indicating position information ofa PUSCH (e.g., the k-th PUSCH among the plurality of PUSCHs allocated bythe UL-DCI) to which the UCI (e.g., HARQ response and/or CSI) is mapped.The UCI mapping indication field may be an index indicating a PUSCH. Forexample, when the UL-DCI assigns k PUSCHs, the size of the UCI mappingindication field included in the corresponding UL-DCI may be ┌log₂(k)┐bits. When a specific field included in the UL-DCI triggers a mappingoperation of the UCI, the terminal may identify the PUSCH in which theUCI is multiplexed based on a combination of the specific field includedin the UL-DCI and the field indicating the time resource to which theUCI is mapped. When the specific field included in the UL-DCI does nottrigger the mapping operation of the UCI, the terminal may ignore thefield indicating the time resource to which the UCI is mapped, which isincluded in the UL-DCI.

The above-described methods may be applied when the UCI is transmittedthrough the PUSCH as being multiplexed with the UL-SCH. Theabove-described methods may not be applied when the PUCCH to which theUCI is mapped is transmitted together with the PUSCH.

In a proposed method, the UL-DCI may indicate a slot to which the UCI ismapped.

The UCI may be transmitted on a PUCCH. A resource of the PUCCH may beindicated by the UL-DCI. For example, the PUCCH resource may beindicated by an explicit scheme or a combination of an explicit schemeand an implicit scheme. The above-described methods may not indicate theslot in which the PUCCH is transmitted. In this case, the slot in whichthe PUCCH is transmitted may be indicated by another method. In aproposed method, a specific field included in the UL-DCI may indicatethe slot in which the PUCCH is transmitted. The slot in which the PUCCHis transmitted may be one of slot(s) to which the PUSCH(s) areallocated.

The PUSCH may occupy a few symbols. Therefore, even when the UL-DCIschedules k PUSCHs, the k PUSCHs may be mapped to k slots or less. Thenumber of slots to which the k PUSCHs are mapped may be changeddynamically, and the size of the field of the UL-DCI may be changed. Inorder to indicate the slot in which the UCI is transmitted, a method ofindicating a relative index of the slot may not be appropriate. Here,the relative index of the slot may indicate the slot in which the UCI(or PUCCH) is transmitted among the slots occupied by the PUSCHs. Thebase station may inform the terminal of the PUSCH in which the UCI istransmitted. In this case, the terminal may transmit the PUCCH based ona time resource derived from a PUCCH resource index in the slot occupiedby the PUSCH indicated by the base station.

According to the above two methods, the terminal may determine whetherto transmit the UCI based on a combination of two fields included in theUL-DCI. In addition, when it is determined that the UCI is transmitted,the terminal may determine the transmission time resource of the UCIbased on a combination of two fields included in the UL-DCI. Accordingto another method, the terminal may determine the transmission timeresource of the UCI based on one field included in the UL-DCI. Forexample, the terminal may use a field indicating the time resource towhich the UCI is mapped instead of the field triggering transmission ofthe UCI. The UL-DCI may include the field that triggers transmission ofthe UCI and the field indicating the time resource to which the UCI ismapped.

In a proposed method, the UL-DCI may include a field indicating oneindex, and the index may indicate both the triggering of thetransmission of the UCI and the time resource to which the UCI ismapped.

According to the above-described method, the field necessary forindicating the UCI transmission may be reduced. Therefore, the size ofthe field required to indicate the UCI transmission in the UL-DCI may bereduced. For example, the index set to a first value may indicate thatUCI transmission is not triggered, and the index set to another valuemay indicate that the UCI transmission is triggered and the position ofthe PUSCH in which the UCI is multiplexed. For example, when the UL-DCIschedules k PUSCHs, the size of the index included in the UL-DCI may be┌log₂(1+k)┐ bits.

The time resource to which the UCI is mapped may be determined based onthe contents defined in the technical specification. In this case, theUL-DCI may not include the field indicating the transmission time pointof the UCI. The UCI may be transmitted on a PUSCH specified in thetechnical specification. Therefore, the size of the UL-DCI may bereduced.

Method of Multiplexing UCI With UL-SCH

When the UL-DCI schedules transmission of two or more PUSCHs and thecorresponding UL-DCI indicates that transmission of UCI is triggered,the terminal may map the UCI to a specific PUSCH. For example, when theUL-DCI schedules transmission of k PUSCHs (e.g., PUSCH #0, . . . , PUSCH#(k-1)), the terminal may map the UCI to the PUSCH #(k-1) or the PUSCH#(k-2). The terminal may transmit the PUSCH after performing the LBToperation. A probability that the LBT operation for each of the k PUSCHssucceeds may increase in a temporal order. This is because the terminalcan transmit the next PUSCH of the current PUSCH when the terminalsucceeds in the LBT operation for the current PUSCH. When the UL-DCIschedules transmission of k PUSCHs (e.g., PUSCH #0, , PUSCH #(k-1)), atransmission probability of the PUSCH #(k-1) is the highest among the kPUSCHs.

In addition, when UL-DCI schedules transmission of k PUSCHs (e.g., PUSCH#0, , PUSCH #(k-1)), a transmission probability of the PUSCH #0 is thelowest among the k PUSCHs. Therefore, the PUSCH #0 may have a shortlength. The terminal may perform the LBT operation from the slot inwhich the PUSCH #0 is located, and may start the PUSCH transmission whenthe LBT operation is successful. When the LBT operation fails, the PUSCHmay not be transmitted. Accordingly, many symbols (e.g., many REs) maybe allocated for the PUSCH #(k-1). Since rate matching is performed forthe UL-SCH when the UCI is multiplexed with the UL-SCH, the UCI may bepreferably mapped to the PUSCH #(k-1) having a relatively large size. .

Meanwhile, the last PUSCH among the PUSCHs allocated by the base stationmay be multiplexed with a SRS in the time domain. The SRS may betransmitted after the last PUSCH. In this case, the PUSCH having thelongest length among the PUSCHs allocated by the base station may not bethe last PUSCH. That is, the length (e.g., the number of symbols) of thelast PUSCH may be shorter than the length of the previous PUSCH of thelast PUSCH. The UCI may be multiplexed with the UL-SCH in the previousPUSCH of the last PUSCH.

Method of Mapping UCI to a PUCCH

The base station may transmit UL-DCI directly or indirectly indicating aPUCCH resource to the terminal. The terminal may receive the UL-DCI fromthe base station, and may identify the PUCCH resource based on theUL-DCI. The slot in which the PUCCH is transmitted may be a slot inwhich a specific PUSCH defined in the technical standard is transmitted.

The slot in which the PUCCH is transmitted may be a slot having a highprobability of success of the LBT operation performed in the terminal.When PUSCHs are allocated in a plurality of slots, the PUCCHtransmission may not be performed in the first slot among the pluralityof slots. The PUCCH transmission may be preferably performed in the lastslot or the previous slot of the last slot among the plurality of slots.The terminal may determine one slot in which the PUCCH is transmittedbased on the contents defined in the technical specification. Theterminal may transmit the UCI to the base station using a PUCCH resourcein the preconfigured slot.

Method of Configuring Resources for a PUCCH

The base station may transmit a resource set or a resource list of aPUCCH to the terminal using an RRC message (e.g., higher layersignaling). A time resource, frequency resource, and sequence resourcefor the PUCCH may be indicated by the following field(s). The terminalmay derive a PUCCH resource based on one index included in a DCIreceived from the base station.

Time Resource of PUCCH Start Symbol Field

The start symbol field may express a start symbol of the PUCCH or thestart symbol and an end symbol of the PUCCH as one index. The terminalmay identify the start symbol of the PUCCH and the number of symbolsbelonging to the PUCCH based on the index indicated by the start symbolfield.

Length Field

The length field may express the number of symbols occupied by the PUCCHas one index.

Frequency Resource of PUCCH Resource Block (RB) Allocation Fields

In order to satisfy the frequency regulation in an unlicensed band, thePUCCH may have a structure of an interlace present in the entirebandwidth. Therefore, the RB allocation field may imply an interlaceindex of the PUCCH.

Meanwhile, when one BWP (e.g., active BWP) is configured to span aplurality of LBT subbands, the PUCCH may be mapped in one of LBTsubband. The base station may inform the terminal of the LBT subband towhich the interlace of the PUCCH belongs as well as the interlace indexof the PUCCH to indicate RBs to which the PUCCH is allocated.Accordingly, the RB allocation field may imply not only the interlaceindex of the PUCCH but also the index of the LBT subband (e.g., RB set)associated with the interlace.

Sequence Resource of PUCCH PUCCH DM-RS Resource Field

The terminal may derive a DM-RS resource based on the PUCCH DM-RSresource field. When the PUCCH DM-RS is generated based on a Zadoff-Chu(ZC) sequence, the terminal may generate a ZC sequence based on a basesequence, and a cyclic shift may be applied to the generated ZCsequence. The base station may inform a cyclic shift to each of theterminals. The terminal may map the sequence to a resource grid definedbased on a ‘point A’.

When the PUCCH DM-RS is generated based on a pseudo random noise (PN)sequence, the terminal may initialize the PN sequence, and map the PNsequence (e.g., initialized PN sequence) to REs defined based on thepoint A. The terminal may know an initialization value of the PNsequence based on information indicated by a field received from thebase station. For example, in the NR communication system, the basestation may inform the terminal of a scrambling value (e.g.,dataScramblingIdentityPUSCH) required for initialization of the PNsequence using higher layer signaling. Alternatively, the terminal mayidentify information necessary for the initialization of the PN sequencebased on cell identification information (e.g., cell ID). The terminalmay initialize the PN sequence based on a combination of informationreceived from the base station (e.g., scrambling value, cellidentification information) and terminal identification information(e.g., RNTI).

PUCCH OCC Field

When the size of the UCI transmitted on the PUCCH is 1 bit or 2 bits,the UCI may be spread based on an OCC in the frequency domain. In thiscase, the base station may transmit a PUCCH OCC field indicating an OCCindex to each of the terminals.

The exemplary embodiments of the present disclosure may be implementedas program instructions executable by a variety of computers andrecorded on a computer readable medium. The computer readable medium mayinclude a program instruction, a data file, a data structure, or acombination thereof. The program instructions recorded on the computerreadable medium may be designed and configured specifically for thepresent disclosure or can be publicly known and available to those whoare skilled in the field of computer software.

Examples of the computer readable medium may include a hardware devicesuch as ROM, RAM, and flash memory, which are specifically configured tostore and execute the program instructions. Examples of the programinstructions include machine codes made by, for example, a compiler, aswell as high-level language codes executable by a computer, using aninterpreter. The above exemplary hardware device can be configured tooperate as at least one software module in order to perform theembodiments of the present disclosure, and vice versa.

While the exemplary embodiments of the present disclosure and theiradvantages have been described in detail, it should be understood thatvarious changes, substitutions and alterations may be made hereinwithout departing from the scope of the present disclosure.

What is claimed is:
 1. A terminal, the terminal comprising: at least oneprocessor, wherein the at least one processor causes the terminal to:receive a radio resource control (RRC) message including firstinformation of a plurality of hybrid automatic repeat request (HARQ)codebooks and second information of a plurality of HARQ processesassociated with each of the plurality of HARQ codebooks from a basestation; receive first downlink control information (DCI) includingfirst scheduling information of a first physical downlink shared channel(PDSCH) from the base station; perform a first reception operation ofthe first PDSCH based on the first DCI; receive second DCI including aHARQ indication field indicating a HARQ codebook among the plurality ofHARQ codebooks indicated by the first information from the base station;identify the plurality of HARQ processes associated with the HARQcodebook indicated by the HARQ indication field based on the secondinformation; generate the HARQ codebook including a first HARQ responsebit of the first PDSCH associated with the plurality of HARQ processes;and transmit uplink control information (UCI) including the HARQcodebook to the base station.
 2. The terminal of claim 1, wherein the atleast one processor further causes the terminal to: receive third DCIincluding second scheduling information of a second PDSCH; and perform asecond reception operation of the second PDSCH based on the third DCI,wherein the HARQ codebook further includes a second HARQ response bit ofthe second PDSCH associated with the plurality of HARQ processes.
 3. Theterminal of claim 2, wherein the first HARQ response bit and the secondHARQ response bit are concatenated in an order of HARQ process numbersin the HARQ codebook.
 4. The terminal of claim 1, wherein the UCI isspread using orthogonal cover code (OCC) in consecutive subcarriers of afrequency domain, and a length of the OCC is
 2. 5. A base station, thebase station comprising: at least one processor, wherein the at leastone processor causes the base station to: transmit a radio resourcecontrol (RRC) message including first information of a plurality ofhybrid automatic repeat request (HARQ) codebooks and second informationof a plurality of HARQ processes associated with each of the pluralityof HARQ codebooks to a terminal; transmit first downlink controlinformation (DCI) including first scheduling information of a firstphysical downlink shared channel (PDSCH) to the terminal; transmit thefirst PDSCH based on the first DCI to the terminal; transmit second DCIincluding a HARQ indication field indicating a HARQ codebook among theplurality of HARQ codebooks indicated by the first information to theterminal; and receive uplink control information (UCI) including theHARQ codebook which includes a first HARQ response bit of the firstPDSCH associated with the plurality of HARQ processes indicated by thesecond information from the terminal.
 6. The base station of claim 5,wherein the at least one processor further causes the base station to:transmit third DCI including second scheduling information of a secondPDSCH to the terminal; and transmit the second PDSCH based on the thirdDCI to the terminal, wherein the HARQ codebook further includes a secondHARQ response bit of the second PDSCH associated with the plurality ofHARQ processes.
 7. The base station of claim 6, wherein the first HARQresponse bit and the second HARQ response bit are concatenated in anorder of HARQ process numbers in the HARQ codebook.
 8. The base stationof claim 5, wherein the UCI is spread using orthogonal cover code (OCC)in consecutive subcarriers of a frequency domain, and a length of theOCC is 2.